Authentication Mechanism for 5G Technologies

ABSTRACT

Embodiments of this disclosure provide techniques for securely communicating an IMSI over the air from a UE to an SeAN, as well as for securely validating an unencrypted IMSI that the SeAN receives from the home network, during authentication protocols. In particular, the UE may either encrypt the IMSI assigned to the UE using an IMSI encryption key (K IMSIenc ) or compute a hash of the IMSI assigned to the UE using an IMSI integrity key (K IMSIint ), and then send the encrypted IMSI or the hash of the IMSI to the serving network. The encrypted IMSI or hash of the encrypted IMSI may then be used by the SeAN to validate an unencrypted IMSI that was previously received from an HSS in the home network of the UE.

This application is a divisional of U.S. application Ser. No.15/670,964, filed on Aug. 7, 2017 which claims priority to both U.S.Provisional Application 62/463,521 filed on Feb. 24, 2017 and U.S.Provisional Application 62/414,488 filed on Oct. 28, 2016, as well as isa continuation-in-part of U.S. Non-Provisional application 15/453,776(Now U.S. Pat. No. 10,382,206) filed on Mar. 8, 2017, which claimspriority to each of U.S. Provisional Application 62/306,550 filed onMar. 10, 2016, U.S. Provisional Application 62/317,295 filed on Apr. 1,2016, U.S. Provisional Application 62/383,223 filed on Sep. 2, 2016,U.S. Provisional Application 62/399,069 filed on Sep. 23, 2016, and U.S.Provisional Application 62/399,055 filed on Sep. 23, 2016, all of whichare incorporated by reference herein as if reproduced in theirentireties.

TECHNICAL FIELD

The present disclosure relates generally to wireless telecommunications,and, in particular embodiments, to a system and method forauthentication mechanisms for 5G technologies while providing privacy tosubscriber and UE permanent identifiers.

BACKGROUND

Modern wireless networks typically include various security features toprevent unauthorized third parties from access and/or manipulating data.In particular, long term evolution (LTE) networks provide three basicsecurity features, namely: LTE authentication, non-access stratum (NAS)security, and access stratum (AS) security. The LTE authenticationfeature ensures that a user is an authorized subscriber to the network(or network service) that the user is attempting to access, while theNAS security and AS security features ensure that control and user datacommunicated over a radio access network (RAN) is secure at the NAS andAS levels, respectively.

SUMMARY

Technical advantages are generally achieved, by embodiments of thisdisclosure which describe authentication mechanisms for 5G technologies.

In accordance with an embodiment, a method for secure authentication isprovided. In this example, the method includes generating a firstintegrity key based at least on a pre-provisioned key (K key) of the UEand a first random number (RAND1), and generating a messageauthentication code (MAC) signature by computing a hash function of UEspecific information using the first integrity key. The UE specificinformation includes at least an International Mobile SubscriberIdentity (IMSI) of the UE and the RAND1. The method further includesencrypting the UE specific information and the MAC signature using apublic key to form an encrypted portion, and sending an initialauthentication request message to a base station in a serving network.The initial authentication request message carrying the encryptedportion and an unencrypted network identifier. An apparatus forperforming this method is also provided.

In accordance with another embodiment, another method for secureauthentication is provided. In this example, the method includesreceiving a user authentication information request message from amobility management entity (MME) in a serving network that includes ahome network identifier (HID) and an encrypted portion, and decryptingthe encrypted portion using a home network private key associated withthe HID to obtain user equipment (UE) specific information and a firstMessage authentication code (MAC) signature. The UE specific informationincludes at least an International Mobile Subscriber Identity (IMSI) ofthe UE and a first random number (RAND1). The method further includesobtaining a first integrity key based on the IMSI of the UE and theRAND1, and verifying the integrity of the user authenticationinformation request message. Verifying the integrity of the userauthentication information request message comprises generating a secondMAC signature by computing a hash function of UE specific informationusing the first integrity key, and comparing the second MAC signaturewith the first MAC signature to determine whether the UE specificinformation originated from the UE. An apparatus for performing thismethod is also provided.

In accordance with yet another embodiment, yet another method for secureauthentication is provided. In this example, the method includesgenerating a first encryption key based on a pre-provisioned key of theUE and a first random number (RAND1), encrypting at least anInternational Mobile Subscriber Identity (IMSI) of the UE and the RAND1using the first encryption key to form an encrypted inner portion,encrypting at least the inner portion, the RAND1, and the IMSI using apublic key to form an encrypted outer portion, and sending an initialauthentication request message to a base station in a serving network.The initial authentication request message carries the encrypted outerportion and an unencrypted network identifier. An apparatus forperforming this method is also provided.

In accordance with yet another embodiment, yet another method for secureauthentication is provided. In this example, the method includesreceiving an initial authentication request message from a userequipment (UE) that includes an encrypted outer portion and anunencrypted network identifier, decrypting the encrypted outer portionusing a private key associated with the serving network to obtain anInternational Mobile Subscriber Identity (IMSI) of the UE, a firstrandom number (RAND1), and an encrypted inner-portion, and sending anauthentication and data request message to a home subscriber server(HSS) in a home network of the UE. The authentication and data requestmessage includes at least the IMSI, RAND1, and the encrypted innerportion. An apparatus for performing this method is also provided.

According to one aspect of the present disclosure, there is provided amethod for secure authentication that includes sending, an encryptedInternational Mobile Subscriber Identity (IMSI) or a hash of the IMSI toa base station in a serving network, the encrypted IMSI or the hash ofthe IMSI having been generated using an IMSI encryption key(K_(IMSIenc)) an IMSI integrity key (K_(IMSIint)) associated with aserving network. In one example, the method of claim further includescomputing a response parameter (RES) based on a pre-provisioned key (Kkey) associated with the UE and a random number (RAND), and sending theRES to the base station in the serving network. Optionally, in any oneof the above mentioned examples, or another example, the K_(IMSIenc) orthe K_(IMSint) is a NAS encryption or integrity key. Optionally, in anyone of the above mentioned examples, or another example, the K_(IMSIenc)or the K_(IMSIint) is derived based on an NG-K_(ASME).

Optionally, in any one of the above mentioned examples, or anotherexample, the K_(IMSIenc), or the K_(IMSIint) is an IAS encryption orintegrity key (K_(IASenc)). Optionally, in any one of the abovementioned examples, or another example the K_(IMSIenc) or theK_(IMSIint) is derived based on pre-provisioned key (“k-key”) assignedto the UE, a COUNTER received from the base station, and a random numberreceived from the base station.

Optionally, in any one of the above mentioned examples, or anotherexample, the K_(IMSIenc) or the K_(IMSIint) is a serving network publickey (SPuK). Optionally, in any one of the above mentioned examples, oranother example, the encrypted IMSI or the Hash of the IMSI is sent tothe base station in an initial authentication response (IAS) message ora user authentication request message.

According to one aspect of the present disclosure, there is provided amethod for secure authentication that includes receiving an unencryptedInternational Mobile Subscriber Identity (IMSI) from a home subscriberserver (HSS) in a home network of a user equipment (UE), receiving, bythe SeAN, an encrypted IMSI or a hash of an IMSI from the UE, andvalidating the unencrypted IMSI received from the HSS in accordance witheither the unencrypted IMSI received from the UE and an IMSI encryptionkey (K_(IMSIenc)) or the hash of the IMSI received from the UE and anIMSI integrity key (K_(IMSIint)). In one example, validating theunencrypted IMSI received from the HSS comprises decrypting theencrypted IMSI received from the UE using the K_(IMSIenc) to obtain adecrypted IMSI, and validating the unencrypted IMSI received from theHSS when the unencrypted IMSI matches the decrypted IMSI. In anotherexample, validating the unencrypted IMSI received from the HSS comprisescomputing a hash of the unencrypted IMSI received from the HSS using theK_(IMSIint), and validating the unencrypted IMSI received from the HSSwhen the computed hash of the unencrypted IMSI matches the hash of theIMSI received from the UE. Optionally, in any one of the above mentionedexamples, or another example, the K_(IMSIenc) or the K_(IMSIint) is aNAS encryption or integrity key. Optionally, in any one of the abovementioned examples, or another example, the K_(IMSIenc) or theK_(IMSIint) is derived based on an NG-K_(ASME). Optionally, in any oneof the above mentioned examples, or another example, the K_(IMSIenc) orthe K_(IMSIint) is an IAS encryption or integrity key (K_(IASenc)).Optionally, in any one of the above mentioned examples, or anotherexample, the K_(IMSIenc) or the K_(IMSIint) is a serving network privatekey (SPuK).

According to one aspect of the present disclosure, there is provided amethod for secure authentication that includes encrypting anInternational Mobile Subscriber Identity (IMSI) of the UE using homenetwork public key (HPuK) associated with a home network of the UE toobtain an HPuK-encrypted IMSI, sending a first initial authenticationrequest (IAR) message carrying the HPuK-encrypted IMSI to a SecurityAnchor Node (SeAN) in a serving network, and receiving an initialauthentication response (IAS) message from the SeAN, the IAS messageincluding an IAR message resend flag. In response to identifying the IARmessage resend flag in the IAS message, the method further includesencrypting, or otherwise computing a hash of, the IMSI using an servingnetwork public key (SPuK) to obtain an K_(IMSIenc)-encrypted IMSI or anK_(IMSIint)-signed hash of the IMSI, and sending a second IAR messagethat includes the K_(IMSIenc)-encrypted IMSI or the K_(IMSIint)-signedhash of the IMSI to the SeAN. In one example, the IAR resend flaginstructs the UE to send IMSI encrypted using the SN SPuK in theSecurity and Authentication Complete message.

According to one aspect of the present disclosure, there is provided amethod for secure authentication that includes sending an attach requestmessage to a Security Anchor Node (SeAN) in a serving network thatrequests access to the serving network, receiving an attach rejectmessage indicating that the attach request has been rejected by the SeANand carrying a message authentication code (MAC) signature, attemptingto validate the received attach reject message by processing the MACsignature carried by the received attach reject message according to aserving network public key (SPuK) assigned to the serving network, andignoring the received attach reject message upon determining that theattach reject message is invalid.

In one example, the SPuK belongs to a public-private key pair associatedwith the serving network, and the signed attach reject message can onlybe successfully validated using the SPuk when the underlying attachreject message was signed using a serving network private key (SPrK) ofthe public-private key pair. Optionally, in any one of the abovementioned examples, or another example, the method further includessetting a back-off timer according to the attach reject message upondetermining that the attempt to validate the attach reject messagesignature using the SPuK is successful, where the UE is unable toinitiate mobility management signaling prior to expiration of theback-off timer. Optionally, in any one of the above mentioned examples,or another example, attempting to validate the integrity of the receivedattach reject message by processing the MAC signature carried by thereceived attach reject message according to the SPuK comprisesgenerating a separate MAC signature by computing a hash function ofinformation carried by the attach reject message according to the SPuK,and comparing the MAC signature generated by the UE with the MACsignature carried by the attach reject message. Optionally, in any oneof the above mentioned examples, or another example, the method furthercomprises receiving a system information message from the SeAN carryingits own a MAC signature, attempting to validate the integrity of thereceived system information message by processing the MAC signaturecarried by the received system information message according to theSPuK, and ignoring the received system information message upondetermining that the system information message is invalid.

According to one aspect of the present disclosure, there is provided amethod for secure authentication that includes encrypting anInternational Mobile Subscriber Identity (IMSI) using a home networkpublic key (HPuK) associated with a home network of the UE, sending aninitial authentication request (IAR) message carrying the encrypted IMSIto a Security Anchor Node (SeAN) in a serving network. The encryptedIMSI is relayed from the SeAN to a home subscriber server (HSS) withoutbeing decrypted. The method further includes receiving an initialauthentication response (IAS) message carrying a home network temporaryidentifier (Home-Temp-ID) from the SeAN, where the Home-Temp-ID wasassigned to the UE by the HSS, and sending a subsequent attach messagecarrying the Home-Temp-ID to the SeAN. In one example, the IAS messagefurther includes a Home-UE-Security-Policy assigned to the UE by theHSS. The Home-UE-Security-Policy indicates how often non-access stratum(NAS) or access stratum (AS) security keys should be updated.

According to one aspect of the present disclosure, there is provided amethod for secure authentication that includes sending a firstauthentication message carrying UE-specific network access stratum (NAS)security capabilities of the UE to a Security Anchor Node (SeAN) in aserving network, receiving a second authentication message from the SeANcarrying NAS layer encryption algorithm supported by the SeAN accordingto at least the UE-specific NAS security capabilities included in thefirst authentication message. In one example, the UE-specific NASsecurity capabilities include a NAS encryption algorithm, a NASintegrity protection algorithm, an RRC encryption algorithm, an RRCintegrity algorithm, a user plane encryption algorithm, a user planeintegrity algorithm, an IMSI concealment algorithm, or combinationsthereof.

According to one aspect of the present disclosure, there is provided amethod for secure authentication that include receiving a firstauthentication message carrying serving network specific (SN-specific)network access stratum (NAS) security capabilities of a serving networkfrom a Security Anchor Node (SeAN) in the serving network, generatingNAS layer encryption keys according to the SN-specific NAS securitycapabilities, and sending a second protected authentication using theNAS layer encryption and integrity keys to the SeAN.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the present disclosure, and theadvantages thereof, reference is now made to the following descriptionstaken in conjunction with the accompanying drawings, in which:

FIG. 1 is a diagram of an embodiment wireless communications network;

FIG. 2 is a diagram of a 5G network architecture;

FIG. 3 is a protocol diagram of a conventional communications sequencefor authenticating a UE in a wireless network;

FIG. 4 is a protocol diagram of an embodiment communications sequencefor authenticating a UE in a wireless network;

FIG. 5 is a diagram of embodiment frame formats for messages exchangedduring the embodiment communications sequence depicted by FIG. 4;

FIG. 6 is a diagram of additional embodiment frame formats for messagesexchanged during the embodiment communications sequence depicted by FIG.4;

FIG. 7 is a flow chart of an embodiment method for generating an initialauthentication request (IAR) message according to a MASA protocol;

FIG. 8 is a flow chart of an embodiment method for processing anauthentication and data request message and generating an authenticationand data response message according to a MASA protocol;

FIG. 9 is a flowchart of an embodiment method for processing anauthentication and data response message and generating an initialauthentication response (IAS) message according to a MASA protocol;

FIG. 10 is a flowchart of an embodiment method for processing an IASmessage according to a MASA protocol;

FIG. 11 is a protocol diagram of another embodiment communicationssequence for authenticating a UE in a wireless network;

FIG. 12 is a diagram of embodiment frame formats for messages exchangedduring the embodiment communications sequence depicted by FIG. 11;

FIG. 13 is a flow chart of an embodiment method for generating an IARmessage according to a MASA protocol;

FIG. 14 is a flow chart of an embodiment method for processing anauthentication and data request message and generating an authenticationand data response message according to a MASA protocol;

FIG. 15 is a flowchart of an embodiment method for processing anauthentication and data response message and generating an IAS messageaccording to a MASA protocol;

FIG. 16 is a flowchart of an embodiment method for processing an IASmessage according to a MASA protocol;

FIG. 17 is a protocol diagram of yet another embodiment communicationssequence for authenticating a UE in a wireless network;

FIG. 18 is a diagram of embodiment frame formats for messages exchangedduring the embodiment communications sequence depicted by FIG. 17;

FIG. 19 is a flow chart of an embodiment method for generating an IARmessage according to a MASA protocol;

FIG. 20 is a flowchart of an embodiment method for processing an IARmessage and generating an authentication and data request messageaccording to a MASA protocol;

FIG. 21 is a flow chart of an embodiment method for processing anauthentication and data request message and generating an authenticationand data response message according to a MASA protocol;

FIG. 22 is a diagram of an embodiment frame formats for an IAR message;

FIGS. 23A-23D are protocol diagrams of yet additional embodimentcommunications sequences for authenticating a UE in a wireless network;

FIG. 24 is a protocol diagram of yet another embodiment communicationssequence for authenticating a UE in a wireless network;

FIG. 25 is a flowchart of an embodiment method for securely transmittingan IMSI to a serving network;

FIG. 26 is a flowchart of an embodiment method for securely validatingan unencrypted IMSI received from a home network of a UE;

FIG. 27 is a flowchart of another embodiment method for securelytransmitting an IMSI to a serving network;

FIG. 28 is a flowchart of another embodiment method for securelyvalidating an unencrypted IMSI received from a home network of a UE;

FIG. 29A-B are protocol diagrams of yet additional embodimentcommunications sequence for authenticating a UE in a wireless network;

FIG. 30 is a protocol diagram of yet another embodiment communicationssequence for authenticating a UE in a wireless network;

FIG. 31 is a flowchart of another embodiment method for securelyvalidating an unencrypted IMSI received from a home network of a UE;

FIG. 32 is a diagram of a communications sequence in which a UEunsuccessfully attempts to attach to a wireless network;

FIG. 33 is a diagram of a communications sequence in which a MITM usesan attach reject message to wage a denial of service attack on a UE;

FIG. 34 is a diagram of a communications sequence in which a UEunsuccessfully attempts to attach to a wireless network;

FIG. 35 is a diagram of a communications sequence in which a MITMunsuccessfully attempts to use an attach reject message to wage a denialof service attack;

FIG. 36 is a flowchart of an embodiment method for processing attachreject messages;

FIG. 37 is a protocol diagram of an embodiment communications sequencefor securely transmitting a UE-specific ID to a serving network;

FIG. 38 is a diagram of embodiment frame formats for messagescommunicated in FIG. 37;

FIG. 39 is a flowchart of an embodiment method for securely transmittinga UE-specific ID to a serving network;

FIG. 40 is a protocol diagram of an embodiment communications sequencefor securely negotiating NAS and/or AS layer security parameters;

FIG. 41 is a protocol diagram of another embodiment communicationssequence for securely negotiating NAS layer security parameters;

FIG. 42 is a flowchart of an embodiment method for NAS layer securityparameter negotiation;

FIG. 43 is a flowchart of another embodiment method for NAS layersecurity parameter negotiation;

FIG. 44 is a flowchart of an embodiment method for AS layer securityparameter negotiation;

FIG. 45 is a flowchart of another embodiment method for AS layersecurity parameter negotiation;

FIG. 46 is a diagram of an embodiment processing system; and

FIG. 47 is a diagram of an embodiment transceiver.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

The making and using of embodiments of this disclosure are discussed indetail below. It should be appreciated, however, that the conceptsdisclosed herein can be embodied in a wide variety of specific contexts,and that the specific embodiments discussed herein are merelyillustrative and do not serve to limit the scope of the claims. Further,it should be understood that various changes, substitutions andalterations can be made herein without departing from the spirit andscope of this disclosure as defined by the appended claims. While theinventive aspects are described primarily in the context of 5G wirelessnetworks, it should also be appreciated that those inventive aspects mayalso be applicable to 4G and 3G wireless networks.

The LTE authentication and NAS security protocols are usually performedsequentially, during which time mutual authentication is establishedbetween the UE and the serving network and NAS layer encryption keys aregenerated. In particular, a UE sends an International Mobile SubscriberIdentity (IMSI) to a mobility management entity (MME) in a servingnetwork. The MME then sends the IMSI to a home subscriber server (HSS)in a home network of the UE, which generates Evolved Packet System (EPS)authentication vectors. The EPS authentication vectors are thencommunicated to the MME, where they are used to authenticate the UE andgenerate NAS layer encryption keys in accordance with an authenticationand key agreement (AKA) procedure. Thereafter, the NAS layer encryptionkeys are used to encrypt signaling exchanged between the UE and the MME.

When using conventional LTE authentication protocols, an unencryptedIMSI is communicated from the UE to the access point. This creates apotential security vulnerability because the IMSI is private informationthat can be exploited by malicious third parties to engage inunauthorized activities, such as tracking the UE and/or engaging denialof service attacks. Accordingly, techniques for securely communicatingthe IMSI during LTE authentication are desired.

Embodiments of this disclosure provide techniques for securelycommunicating an IMSI over the air from a UE to an SeAN, as well as forsecurely validating an unencrypted IMSI that the SeAN receives from thehome network, during authentication protocols. In particular, the UE mayeither encrypt the IMSI assigned to the UE using an IMSI encryption key(K_(IMSIenc)) or compute a hash of the IMSI assigned to the UE using anIMSI integrity key (K_(IMSIint)), and then send the encrypted IMSI orthe hash of the IMSI to the serving network. The encrypted IMSI or hashof the encrypted IMSI may then be used by the SeAN to validate anunencrypted IMSI that was previously received from an HSS in the homenetwork of the UE. These and other aspects are explained in greaterdetail below.

Aspects of this disclosure provide embodiment mutual authentication andsecurity agreement (MASA) protocols that use independently generatedintegrity and/or encryption keys to securely communicate privateinformation exchanged between UEs and various network-side devices(e.g., base stations, MMEs, HSSs, etc.). In particular, embodiment MASAprotocols may use an initial authentication request (IAR) encryption key(KIAR_(ENC)) to encrypt UE specific information (e.g., an IMSI, etc.) inan IAR message and/or an initial authentication response (IAS)encryption key (KIAS_(ENC)) to encrypt private information in an IASmessage. Additionally, embodiment MASA protocols may use an IARintegrity protection key (KIAR_(INT)) to verify the integrity ofinformation in an IAR message and/or an IAS integrity protection key(KIAS_(INT)) to verify the integrity of information in an IAS message.The KIAR_(ENC), KIAR_(INT), KIAS_(ENC), and/or KIAS_(INT) may beindependently computed by the UE and a home subscriber server (HSS)based on, for example, a pre-provisioned key (K-key) of the UE and oneor more random numbers (e.g., RAND1, RAND2, UE random number(RAND_(uE)), home network random number (RAND_(HN)), and/or a COUNTER.Using a COUNTER to compute an instance of a given key may be useful inensuring that each generated instance of the key differs from previousgenerated instances of the key, as it is possible that the same randomnumber could be selected to generate different instances of a key, whichcould constitute a security vulnerability.

Different levels of encryption and/or integrity protection can beachieved depending on the complexity of the embodiment MASA protocol. Inone embodiment, a low complexity MASA protocol use integrity keys (e.g.,a KIAR_(INT) and/or a KIAS_(INT)) to provide integrity protection whencommunicating IAR and/or IAS messages having a single layer ofencryption protection. In particular, a UE may encrypt UE specificinformation (e.g., an IMSI, random numbers, etc.) using a home networkpublic key (HPuK) to form an encrypted portion, and then generate amedia access control (MAC) signature by computing a hash function of theencrypted portion, and potentially additional information (e.g., arandom number) in an outer portion of the IAR message, using aKIAR_(INT). The UE may then send an IAR message carrying the encryptedportion and the MAC signature to a base station in a serving network,which may relay the IAR message to an MME. The MME may encapsulate theIAR message into a user authentication data request message, which maythen be sent to a home subscriber server (HSS) in the UE's home network.The HSS may independently compute a MAC signature of the contents of theIAR message based on an independently generate integrity key (e.g., theKIAR_(INT)), and then compare the independently generated MAC signaturewith the MAC signature included in the IAR message to verify theintegrity of the encrypted portion of the IAR message. A similarprocedure can be used to provide integrity protection for the IASmessage.

In another embodiment, a higher complexity MASA protocol uses encryptionkeys (e.g., KIAR_(ENC) and/or KIAS_(ENC)) in conjunction with the homenetwork public-private key pair to provide two layers of encryption forthe contents of IAR and/or IAS messages. In particular, a UE may use apre-provisioned key and a first random number (RAND1) to generate aninitial authentication request encryption key (KIAR_(ENC)). TheKIAR_(ENC) is then used to encrypt private information to form anencrypted inner portion of an authentication request message. Theprivate information may include the IMSI of the UE, the RAND1, a secondrandom number (RAND2), UE-Security-Capabilities, and/or a counter. Next,the UE may encrypt the RAND1, the IMSI, and the encrypted inner portionto obtain an encrypted outer portion of the authentication requestmessage. Other information may also be encrypted when generating theencrypted outer portion. The public key used to generate the encryptedouter portion may belong to a private-public-key-pair. In oneembodiment, the public key is a home network public key (HPuK). Inanother embodiment, the public key is a serving network public key(SPuK). Thereafter, the UE may send the authentication request messagecarrying the encrypted outer portion and an unencrypted networkidentifier to an MME in the serving network. If the public key used togenerate the encrypted outer portion was a SPuK, then the unencryptednetwork identifier in the authentication request message may be aserving network identifier (SID). In that case, the MME may use aserving network private key to decrypt the encrypted outer portion andobtain the RAND1, the IMSI, and the encrypted inner portion, which maythen be forwarded to a home subscriber server (HSS) in a home network ofthe UE. Alternatively, if the public key used to generate the encryptedouter portion was a HPuK, then the unencrypted network identifier in theauthentication request message may be a home network identifier (HID).In that case, the MME would send an authentication and data requestcarrying the encrypted outer portion, along with the HID, MME securitycapability identifiers, to the HSS in the home network. The HSS wouldthen decrypt the encrypted outer portion using a home network privatekey and obtain the RAND1, the IMSI, and the encrypted inner portion.

In both cases, the HSS would then use the RAND1 and a K key associatedwith the UE to independently generate the KIAR_(ENC), which the HSSwould subsequently use to decrypt the encrypted inner portion. The HSSwould then verify that IMSI in the decrypted inner portion matched theIMSI in the decrypted outer portion to verify that the encrypted outerportion had not been tampered with by an unauthorized third party.Thereafter, the HSS may verify that the counter in the decrypted innerportion matched a counter maintained by the HSS initial authenticationrequest (IAR) was fresh (i.e., not stale). If the validations weresuccessful, then the HSS may generate an initial authentication responseencryption key (KIAS_(ENC)) based on the RAND2 and the K key associatedwith the IMSI. The HSS may also generate one or more authenticationvectors. The HSS may then send an initial authorization and dataresponse to the MME that includes the KIAS_(ENC) and the authenticationvectors. In some embodiments, the initial authorization and dataresponse includes a UE security capability parameter. The MME may thenselect one of the authentication vectors, as well as a non-accessstratum (NAS) ciphering algorithm. The MME may also assign a temporarynetwork identifier (e.g., a globally unique temporary identifier (GUTI))to the UE. Thereafter, the MME may encrypt the KIAS_(ENC), the temporarynetwork identifier, and a key set identifier (KSI) associated with theselected NAS ciphering algorithm using the KIAS_(ENC) to obtainencrypted NAS security data. The encrypted NAS security data may includeother information as well, such as the counter and the RAND2. The MMEmay then send an initial authentication and data response to the UEcarrying the encrypted NAS security data as well as an unencryptedRAND2. The UE may then independently generate the KIAS_(ENC) based onthe RAND2 and the K key. The UE may then generate a ciphering key usingthe NAS ciphering algorithm associated with the KSI in the decrypted NASsecurity data. The UE may then return a security authentication completemessage to the MME, confirming that the serving network has beenauthenticated. Encrypting the IMSI, as well as the temporary network ID,in the manner described herein allows that information to be securelyexchanged during LTE authentication and NAS security protocols.Additionally, the embodiment procedures described herein reduce thenumber of messages exchanged between the UE and the base station duringLTE authentication and NAS security protocols. These and other detailsare discussed in greater detail below.

FIG. 1 illustrates a network loo for communicating data. The network loocomprises a base station no having a coverage area 101, a plurality ofmobile devices 115, and a backhaul network 130. As shown, the basestation no establishes uplink (dashed line) and/or downlink (dottedline) connections with the mobile devices 115, which serve to carry datafrom the mobile devices 115 to the base station no and vice-versa. Datacarried over the uplink/downlink connections may include datacommunicated between the mobile devices 115, as well as datacommunicated to/from a remote-end (not shown) by way of the backhaulnetwork 130. As used herein, the term “base station” refers to anycomponent (or collection of components) configured to provide wirelessaccess to a network, such as an enhanced base station (eNB), amacro-cell, a femtocell, a Wi-Fi access point (AP), or other wirelesslyenabled devices. Base stations may provide wireless access in accordancewith one or more wireless communication protocols, e.g., long termevolution (LTE), LTE advanced (LTE-A), High Speed Packet Access (HSPA),Wi-Fi 802.11a/b/g/n/ac, etc. As used herein, the term “mobile device”refers to any component (or collection of components) capable ofestablishing a wireless connection with a base station, such as a userequipment (UE), a mobile station (STA), and other wirelessly enableddevices. In some embodiments, the network loo may comprise various otherwireless devices, such as relays, low power nodes, etc.

FIG. 2 illustrates a network architecture 200 for a 5G LTE wirelessnetwork. As shown, the network architecture 200 includes a radio accessnetwork (RAN) 201, an evolved packet core (EPC) 202, and a home network203 of a UE 215 attempting to access the RAN 201. The RAN 201 and theEPC 202 form a serving wireless network. The RAN 201 includes a basestation 210, and the EPC 202 includes a Security Anchor Node (SeAN) 220,a serving gateway (SGW) 222, and a packet data network (PDN) gateway(PGW) 224. The SeAN 220 is the termination point in the network forciphering/integrity protection for NAS signaling and handles thesecurity key management. It should be appreciated that the SeAN 220 mayperform similar functions, and have similar responsibilities, as aMobility Management Entity (MME) and/or a Security Access Function(SeAF), such as providing a control plane function for mobility betweenLTE and 2G/3G access networks, as well as providing an interface to homenetworks of roaming UEs. Because of those similarities, the terms “MME,”“SeAN,” and “SEAF” are used interchangeably throughout this document.The SGW 222 routes and forwards user data packets, while also acting asa mobility anchor for the user plane during handovers. The PGW 224provides connectivity from UEs to external packet data networks by beingthe point of exit and entry of traffic for the UEs. The HSS 230 is acentral database that contains user-related and subscription-relatedinformation.

Conventional LTE authentication protocols communicate an unencryptedIMSI of the UE over the radio access network, which presents securityvulnerability. FIG. 3 illustrates a protocol diagram of a conventionalcommunications sequence 300 for authenticating the UE 215 in a wirelessnetwork. As shown, the communications sequence 300 begins when the SeAN220 communicates an identity request 310 to the UE 215. Next, the UE 215communicates an identity response 320 to the SeAN 220. The identityresponse 320 includes an unencrypted IMSI of the UE 215. Thereafter, theSeAN 220 communicates an authorization data request 330 to the HSS 230.The authorization data request 330 may include the IMSI. The HSS 230then computes EPS authentication vectors, and sends an authorizationdata response 335 carrying the EPS authentication vectors to the SeAN220. Subsequently, the SeAN 220 communicates a user authenticationrequest 340 to the UE 215. The user authentication request 340 ncludes arandom number (RAND) and an authentication parameter (AUTN). The UE 215computes an authentication response (RES) based on the RAND, AUTN, and asecret key. The secret key may be a priori information to the UE 215.For example, the secret key (e.g., a subscriber-specific master key (K))may be stored in a Universal Subscriber Identity Module (USIM) of the UE215. The UE 215 may then send a user authentication response 350carrying the authentication response (or RES) to the SeAN 220.

Thereafter, the SeAN 220 communicates a security mode command message360 to the UE 215. The security mode command message 360 may indicate anintegrity protection algorithm and a ciphering algorithm. The UE 215 mayuse the integrity protection algorithm to verify the integrity of thesecurity mode command message 360. After verifying the integrity of thesecurity mode command message 360, the UE 215 uses the cipheringalgorithm to derive NAS encryption keys. The UE 215 then sends thesecurity mode complete message 370 to the SeAN 220 to verify that the UE215 validated the security mode command message 360, and derived the NASencryption keys.

In some instances, a third party may eavesdrop on the communicationssequence 300 in an attempt to intercept one or more of the messages310-370. If the identity response 320 is intercepted, then the thirdparty may use the unencrypted IMSI to perform unauthorized activities,such as to track the UE 215.

Aspects of this disclosure prevent, or at least inhibit, unauthorizedthird parties from obtaining an IMSI of a UE during LTE authenticationby encrypting the IMSI using a public key. The public key may be a partof a public-private key pair such that information encrypted with thepublic key can only be decrypted with the private key. In one example,the public key is a home network public key, and the encrypted IMSI isdecrypted by an HSS in the home network of the UE using a home networkprivate key. In such an example, the home network public key may be apriori information of the UE, e.g., the home network public key may bestored in a USIM of the UE. In another example, the public key is aserving network public key (SPuK), and the encrypted IMSI is decryptedby an SeAN in the serving network using a serving network private key.Other examples are also possible.

FIG. 4 illustrates a protocol diagram of an embodiment communicationssequence 400 for authenticating a UE 215 in a wireless network. Asshown, the communications sequence 400 begins when the SeAN 220communicates an identity request 410 to the UE 215. Upon receiving theidentity request 410, the UE 215 generates a MAC signature by computinga hash of UE specific information (e.g., an IMSI, a RAND1, etc.) using aKIAR_(INT), and then encrypts the UE specific information along with theMAC signature using a HPuK to obtain an encrypted portion. The UE 215sends an initial authentication request (IAR) message 420 carrying theencrypted portion to the base station 210, which relays the IAR message420 to the SeAN 220. The IAR message 420 l may also include aunencrypted home network ID (HID) of the home network of the UE 215.

Upon receiving the IAR message 420, the SeAN 220 may identify the homenetwork of the UE 215 based on the unencrypted HID, and communicate anauthentication and data request message 430 to the HSS 230 in theidentified home network. Upon receiving the authentication and datarequest message 430, the HSS 230 may decrypt encrypted portion using aHPrK, and verify the integrity of the encrypted portion based on the MACsignature. In one example, the HSS 230 independently generates a MACsignature by computing a hash of the information in the authenticationand data request message 430 using an independently generated integritykey (e.g., a KIAR_(INT)), and then compares the independently generatedMAC signature with the MAC signature carried by the encrypted portion inthe authentication and data request 430. The HSS 230 may also takefurther steps to validate the encrypted portion. For example, the HSS230 may verify that a COUNTER in the encrypted portion of theauthentication and data request message 430 (e.g., a counter originallyin the IAR message 420) exceeds an independent COUNTER maintained by theHSS 230 in order to confirm that the encrypted portion in theauthentication and data request message 430 is fresh (e.g., not stale).If the encrypted portion is stale, then it may have been intercepted bya malicious man-in-the-middle entity.

After verifying the integrity of the encrypted portion(s), the HSS 230may generate authentication vectors based on an EPS-AKA procedure, andsend an authentication and data response message 435 carrying the EPSauthentication vectors to the SeAN 220. The authentication and dataresponse message 435 may include other information in addition to theEPS authentication vectors, such as integrity/encryption keys (e.g., aKIAS_(INT), KIAS_(ENC), etc.), the IMSI of the UE, a COUNTER, and/or aUE security capabilities. The UE security capabilities may indicateprotocol capabilities supported by the UE, such as,for example, NASciphering algorithms supported by the UE.

The SeAN 220 may then send an initial authentication response (IAS)message 450 to the UE 215. The IAS message 450 may have variousdifferent frame formats, and the contents of the IAS message 450 mayvary depending on the frame format being used. In one example, the IASmessage 450 includes encrypted NAS security data and a key setidentifier (KSI) associated with a NAS ciphering algorithm. The UE 215may use the NAS ciphering algorithm along with an independentlygenerated encryption key (e.g., a KIAS_(ENC)) to decrypt the encryptedNAS security data. After decrypting the encrypted NAS security data, theUE 215 may send a security and authentication complete message 470 tothe SeAN 220.

As mentioned above, the IAR message 420, the authentication and datarequest message 430, the user authentication information responsemessage 435, and the IAS message 450 may have various different frameformats. FIG. 5 illustrates frame formats for an embodiment IAR message520, an embodiment authentication and data request message 530, anembodiment authentication and data response message 535, and anembodiment IAS message 550.

The embodiment IAR message 520 corresponds to the IAR message 420 sentfrom the UE 215 to the SeAN 220. In this example, the embodiment IARmessage 520 includes UE Specific information (UE_info), a MAC signature,and a home network identifier (HID). The UE_info may include variousinformation associated with, or generated by, the UE, including (but notlimited to) an IMSI, one or more random numbers (e.g., RAND1, RAND2,etc.), a counter, and/or UE security capability parameters. The MACsignature may be generated by computing a hash function of the UE_infoaccording to an integrity key (e.g., a KIAR_(INT)) and/or a randomnumber (e.g., RAND1). The MAC signature and the UE_info are encryptedusing a HPuK to form an encrypted portion 522 of the embodiment IARmessage 520.

The embodiment authentication and data request message 530 correspondsto the authentication and data request message 430 sent from the SeAN220 to the HSS 230. As shown, the embodiment authentication and datarequest message 530 includes the embodiment IAR message 520 and an HID.

The embodiment authentication and data response message 535 correspondsto the authentication and data response message 435 sent from the HSS230 to the SeAN 220. As shown, the user authentication informationresponse message 535 includes UE_info (e.g., an IMSI, counter, RAND1,RAND2, UE security capabilities, etc.), as well as authenticationvectors (AVs), a KIAS_(ENC), and a KIAS_(INT).

The embodiment IAS message 550 corresponds to the IAS message 450 sentfrom the SeAN 220 to the UE 215. As shown, the IAS message 450 includesan encrypted inner portion 552, an outer portion 554, and a MAC 556. Theencrypted inner portion 552 is formed by encrypting the AVs using aKIAS_(ENC). It should be appreciated that the encrypted inner portion552 may include other information (e.g., a KSI) in addition to the AVs.The outer portion 554 includes a RAND2 and the encrypted inner portion552. The MAC signature 556 is generated by computing a hash of the outerportion 554 using the KIAS_(INT).

Other frame formats are also possible. FIG. 6 illustrates frame formatsfor an embodiment IAR message 620, an embodiment authentication and datarequest message 630, an embodiment authentication and data responsemessage 635, and an embodiment IAS message 650.

The embodiment IAR message 620 corresponds to the IAR message 420 sentfrom the UE 215 to the SeAN 220. In this example, the embodiment IARmessage 620 includes an encrypted portion 622 and a home networkidentifier (HID). The encrypted portion 622 is generated by using anHPuK to encrypt a UE security capability parameter (UE_SEC_CAP), anIMSI, a RAND1, a RAND2, a COUNTER, and a MAC signature. The MACsignature is generated by computing by using a KIAR_(INT) to compute ahash of the UE_SEC_CAP, the IMSI, the RAND1, the RAND2, and the COUNTER.

The embodiment authentication and data request message 630 correspondsto the authentication and data request message 430 sent from the SeAN220 to the HSS 230. As shown, the embodiment authentication and datarequest message 630 includes the embodiment IAR message 620 and an HID.

The embodiment authentication and data response message 635 correspondsto the authentication and data response message 435 sent from the HSS230 to the SeAN 220. As shown, the authentication and data responsemessage 635 includes a KIAS_(ENC), a KIAS_(INT), AV(s), a UE_SEC_CAP, anIMSI, a RAND1, a RAND2, and a COUNTER.

The embodiment IAS message 650 corresponds to the IAS message 450 sentfrom the SeAN 220 to the UE 215. As shown, the IAS message 450 includesan encrypted inner portion 652, an outer portion 654, and a MACsignature 656. The encrypted inner portion 652 is formed by encrypting aKSI, and a RAND∥AUTN using the KIAS_(ENC). The RAND∥AUTN may specify twoor more parameters included in, or derived by the AVs, and may be usedby the UE to authenticate the network and generate a response, e.g., thesecurity and authentication complete message 470, etc. It should beappreciated that the encrypted inner portion 652 may include other UEspecific information. The outer portion 654 includes a RAND2 and theencrypted inner portion 652. The MAC signature 656 is generated bycomputing a hash of the outer portion 654 using the KIASINT.

Embodiments of this disclosure provide methods for performing MASAprotocols. FIG. 7 is a flowchart of an embodiment method 700 forgenerating an IAR message according to a MASA protocol, as may beperformed by a UE. At step 710, the UE generates a KIAR_(INT) based on apre-provisioned key (K key) and a first random number (RAND1). At step720, the UE generates a MAC signature by computing a hash function of UEspecific information using the KIAR_(INT). The UE specific informationincludes at least an IMSI of the UE and the RAND1. At step 730, the UEencrypts the UE specific information and the MAC signature using a homenetwork public key (HPuK) to form an encrypted portion. The HPuK belongsto a public-private key pair such that the encrypted portion can only bedecrypted using a home network private key (HPrK) belonging to thepublic-private key pair. At 740, the UE sends an IAR message carryingthe encrypted portion and an unencrypted home network identifier (HID)to a base station in a serving network. The base station relays the IARmessage to an SeAN, which sends an authentication and data requestmessage that includes the encrypted portion of the IAR message to an HSSserver in a home network associated with the unencrypted networkidentifier sin the IAR message.

FIG. 8 is a flowchart of an embodiment method 800 for processing anauthentication and data request message and generating an authenticationand data response message according to a MASA protocol, as may beperformed by an HSS. At step 810, the HSS receives an authentication anddata request message from an SeAN in a serving network. Theauthentication and data request message carries an encrypted portion.

At step 820, the HSS decrypts the encrypted portion using a HPrK toobtain a first MAC signature and UE-specific information. TheUE-specific information includes at least an IMSI and a RAND1. At step830, the HSS obtains a KIAR_(INT) based on the IMSI and the RAND1. Inone example, the HSS obtains the KIAR_(INT) by sending the IMSI and theRAND1 to an authentication server, which looks up a pre-provisioned key(K-key) based on the IMSI, generates the KIAR_(INT) based on the K-keyand the RAND1, and returns the KIAR_(INT) to the HSS. At step 840, theHSS verifies the integrity of the encrypted portion based on theKIAR_(INT). In particular, the HSS generates a second MAC signature bycomputing a hash of UE-specific information in the encrypted portionaccording to the KIAR_(INT), and then compares the second MAC signaturewith the first MAC signature. If the MAC signatures match, then theintegrity of the encrypted portion is verified.

At step 850, the HSS generates authentication vectors (AVs) based on anEPS-AKA procedure. At step 860, the HSS obtains a KIAS_(INT) and aKIAS_(ENC) based on the IMSI of the UE and a RAND2. In one example, theHSS obtains the KIAS_(INT) and the KIAS_(ENC) by sending the IMSI andthe RAND2 to an authentication server. The authentication server looksup a pre-provisioned key (K-key) based on the IMSI, generates theKIAS_(INT) and the KIAS_(ENC) based on the K-key and the RAND2, andreturns the KIAS_(INT) and the KIAS_(ENC) to the HSS. In someembodiments, steps 830 and 860 are performed in parallel such that theIMSI, RAND1, and RAND2 are sent from the HSS to the authenticationserver in the same request message, and the KIAR_(INT), KIAS_(ENC), andKIAS_(INT) are returned from the authentication server to the HSS in thesame response message. At step 870, the HSS sends an authentication anddata response message to the SeAN. The authentication and data responsemessage includes the KIAS_(INT), the KIAS_(ENC), the AVs, and UE info.In some embodiments, a COUNTER is also used when generating KIAR_(INT),KIAS_(INT), and KIAS_(ENC).

FIG. 9 is a flowchart of an embodiment method 900 for processing anauthentication and data response message and generating an IAS messageaccording to a MASA protocol, as may be performed by an SeAN. At step910, the SeAN receives an authentication and data response message froman HSS that includes a KIAS_(INT), a KIAS_(ENC), AVs, and user specificinformation. The user specification information may include a UEsecurity capabilities parameter, an IMSI, a RAND2, and/or a COUNTER.

At step 920, the SeAN encrypts the user specific information using theKIAS_(ENC) to obtain an encrypted portion. At step 930, the SeANgenerates a MAC signature by computing a hash of the encrypted portionand the RAND2 based on the KIAS_(INT). At step 940, the SeAN sends anIAS message to a UE that includes at least the encrypted portion, theRAND2, and MAC signature.

FIG. 10 is a flowchart of an embodiment method woo for processing an IASmessage according to a MASA protocol, as may be performed by a UE. Atstep 1010, the UE receives an IAS message from a base station in aserving network. The IAS message includes at least an encrypted portion,a RAND2, and a first MAC signature. At step 1020, the UE computes aKIAS_(INT) and a KIAS_(ENC) based on a K-key of UE and the RAND2. Insome embodiments, step 1020 and 720 may be performed in parallel (e.g.,by a SIM card in the UE) prior to sending an initial IAR message. Atstep 1030, the UE generates a second MAC signature by computing a hashof the encrypted portion and the RAND2 based on the KIAS_(INT). At step1040, the UE verifies that the second MAC signature matches the firstMAC signature in the IAS message. At step 1050, the UE decrypts theencrypted portion using the KIAS_(ENC). At step 1060, the UE sends asecurity and authentication complete message to the SeAN confirming thatthe network has been authenticated.

Aspects of this disclosure prevent, or at least inhibit, unauthorizedthird parties from obtaining an IMSI of a UE during LTE authenticationby encrypting the IMSI using a KIAR_(ENC). FIG. 11 illustrates aprotocol diagram of an embodiment communications sequence 1100 forauthenticating a UE in a wireless network. As shown, the communicationssequence 1100 begins when the SeAN 220 communicates an identity request1110 to the UE 215. Next, the UE 215 encrypts a first copy of the IMSIusing a KIAR_(ENC) to form an encrypted inner portion, and encrypts asecond copy of the IMSI and the encrypted inner portion using an HPuK toform an encrypted outer portion. It should be appreciated that other UEspecific information (e.g., RAND1, RAND2, COUNTER, UE_SEC_CAP, etc.) maybe encrypted along with the IMSI when forming the encrypted innerportion and/or the encrypted outer portion. Thereafter, the UE sends anIAR message 1120 carrying the encrypted outer portion to the SeAN 220.In some embodiments, the UE 215 sends the IAR message 1120 withouthaving received the identity request 1110. The IAR message 1120 mayinclude an unencrypted home network ID (HID) of the home network of theUE 215. Upon receiving the IAR message 1120, the SeAN 220 forwards anauthentication and data request message 1130 carrying the encryptedouter portion to the HSS 230. The authentication and data requestmessage 1130 may include other information in addition to the encryptedouter portion, such as SeAN security capability parameters that identifythe NAS security capabilities of the SeAN 220, e.g., which NAS cipheringalgorithms are supported by the SeAN 220. The authentication and datarequest 1130 may also include a serving network identifier (SID) andnetwork type (NWK Type) of the serving network of the SeAN 220.

Upon receiving the authentication and data request message 1130, the HSS230 may decrypt the encrypted outer portion using a HPrK to obtain thesecond copy of the IMSI and the encrypted inner portion. The HSS 230 maythen decrypt the encrypted inner portion using the KIAR_(ENC) to obtainthe first copy of the IMSI. In some embodiments, the HSS 230 validatesthe authentication and data request message 1130 by comparing the firstcopy of IMSI with the second copy of the IMSI. The HSS 230 may alsocompare the COUNTER with a corresponding COUNTER maintained by the HSS230 to determine whether the authentication and data request 1130 isfresh (e.g., not stale). If the validation is successful, then the HSS230 generates authentication vectors based on an EPS-AKA procedure, andsends an authentication and data response message 1135 carrying the EPSauthentication vectors and a KIAS_(ENC) to the SeAN 220.

Subsequently, the SeAN 220 selects one of the authentication vectors, aswell as a non-access stratum (NAS) ciphering algorithm. The SeAN 220 mayalso assign a temporary network identifier (e.g., a globally uniquetemporary identifier (GUTI)) to the UE. Thereafter, the SeAN 220 mayencrypt, the temporary network identifier, and a key set identifier(KSI) associated with the selected NAS ciphering algorithm using theKIAS_(ENC) to obtain encrypted NAS security data. The encrypted NASsecurity data may include other information as well, such as the counterand the RAND2. The encrypted NAS security data may be included in theIAS message 1150 sent by the SeAN 220 to the UE 215. The IAS message1150 may further include an unencrypted version of the RAND2. The UE 215may authenticate the network by comparing RAND2 to a local version ofRAND2 stored by the UE 215 and by decrypting the encrypted privateinformation of the Authentication Response using the KIAS_(ENC) key. TheUE 215 then sends a security and authentication complete message 1170 tothe SeAN 220.

FIG. 12 illustrates frame formats for an embodiment TAR message 1220, anembodiment authentication and data request message 1230, an embodimentauthentication and data response message 1235, and an embodiment IASmessage 1250.

The embodiment IAR message 1220 corresponds to the IAR message 1120 sentfrom the UE 215 to the SeAN 220. In this example, the embodiment IARmessage 1220 includes an encrypted inner portion 1222, an encryptedouter portion 1224, and an HID. The encrypted inner portion 1222 isformed by encrypting a UE_SEC_CAP, a first copy of an IMSI, a first copyof a RAND1, a RAND2, and a COUNTER using a KIAR_(ENC). The encryptedouter portion 1224 is generated by encrypting the encrypted innerportion 1222 along with a second copy of the IMSI and a second copy ofthe RAND1 using a HPuK. It should be appreciated that additionalinformation may be included in the encrypted inner portion 1222 and/orthe encrypted outer portion 1224.

The embodiment authentication and data request message 1230 correspondsto the authentication and data request message 1130 sent from the SeAN220 to the HSS 230. As shown, the embodiment authentication and datarequest message 1230 includes the embodiment IAR message 1220 and anHID.

The embodiment authentication and data response message 1235 correspondsto the authentication and data response message 1135 sent from the HSS230 to the SeAN 220. As shown, the authentication and data responsemessage 1235 includes a KIAS_(ENC), the UE_SEC_CAP, the IMSI, the RAND2,and the COUNTER.

The embodiment IAS message 1250 corresponds to the IAS message 1150 sentfrom the SeAN 220 to the UE 215. As shown, the IAS message 1150 includesan encrypted portion 1252 and the RAND2. The encrypted portion 1252 isformed by encrypting a KSI, the AVs, and the COUNTER using theKIAS_(ENC).

Embodiments of this disclosure provide methods for performing MASAprotocols. FIG. 13 is a flowchart of an embodiment method 1300 forgenerating an IAR message according to a MASA protocol, as may beperformed by a UE. At step 1310, the UE generates a KIAR_(ENT) based ona pre-provisioned key (K key) and a RAND1. At step 1320, the UE encryptsUE specific information using the KIAR_(ENC) to form an encrypted innerportion. At step 1330, the UE encrypts at least the encrypted innerportion, a RAND1, and an IMSI using an HPuK to form an encrypted outerportion. At step 1340, the UE sends an IAR message carrying theencrypted outer portion and an unencrypted HID to a base station in aserving network.

FIG. 14 is a flowchart of an embodiment method 1400 for processing anauthentication and data request message and generating an authenticationand data response message according to a MASA protocol, as may beperformed by an HSS. At step 1410, the HSS receives an authenticationand data request message from a SeAN in a serving network. Theauthentication and data request message carries an encrypted outerportion.

At step 1420, the HSS decrypts the encrypted portion using an HPrK toobtain a first MAC signature and UE-specific information. TheUE-specific information includes at least an IMSI and a RAND1. At step1430, the HSS obtains a KIAR_(ENC) based on the IMSI and the RAND1. Atstep 1440, the HSS decrypts the encrypted inner portion using theKIAR_(ENC) to obtain UE specific information. At step 1450, the HSSgenerates authentication vectors (AVs) based on an EPS-AKA procedure. Atstep 1460, the HSS obtains a KIAS_(ENC) based on the IMSI and a RAND2.In some embodiments, steps 1430 and 1460 are performed in parallel suchthat the IMSI, RAND1, and RAND2 are sent from the HSS to theauthentication server in the same request message, and the KIAR_(ENC)and KIAS_(ENC) are returned from the authentication server to the HSS inthe same response message. At step 1470, the HSS sends an authenticationand data response message to the SeAN. The authentication and dataresponse message includes the KIAS_(INT), the KIAS_(ENC), the AVs, andUE info.

FIG. 15 is a flowchart of an embodiment method 1500 for processing anauthentication and data response message and generating an IAS messageaccording to a MASA protocol, as may be performed by an SeAN. At step1510, the SeAN receives an authentication and data response message froman HSS that includes a KIAS_(ENC), AVs, and user specific information.The user specification information may include a UE securitycapabilities parameter, an IMSI, a RAND2, and/or a COUNTER.

At step 1520, the SeAN encrypts at least the user specific informationand the AVs using the KIAS_(ENC) to obtain an encrypted portion. Itshould be appreciated that the encrypted portion may include otherinformation, such as a KSI. At step 1530, the SeAN sends an IAS messageto a UE that includes at least the encrypted portion.

FIG. 16 is a flowchart of an embodiment method 1600 for processing anIAS message according to a MASA protocol, as may be performed by a UE.At step 1610, the UE receives an IAS message from a base station in aserving network. The IAS message includes at least an encrypted portion,a RAND2, and a first MAC signature. At step 1620, the UE computes aKIAS_(INT) and a KIAS_(ENC) based on a K-key of UE and the RAND2. Insome embodiments, step 1620 and 1310 may be performed in parallel (e.g.,by a SIM card in the UE) prior to sending an initial IAR message. Atstep 1630, the UE decrypts the encrypted portion using the KIAS_(ENC).At step 1640, the UE sends a security and authentication completemessage to the SeAN confirming that the network has been authenticated.

In some embodiments, the UE uses a serving network public key (SPuK) toencrypt a portion of an IAR message. FIG. 17 illustrates a protocoldiagram of an embodiment communications sequence 1700 for authenticatinga UE in a wireless network. As shown, the communications sequence 1700begins when the SeAN 220 communicates an identity request 1710 to the UE215. Next, the UE 215 encrypts a first copy of an IMSI using aKIAR_(ENC) to form an encrypted inner portion, and encrypts a secondcopy of the IMSI and the encrypted inner portion using a SPuK to form anencrypted outer portion. It should be appreciated that other UE specificinformation (e.g., a RAND1, a RAND2, a COUNTER, a UE_SEC_CAP, etc.) maybe encrypted along with the IMSI when forming the encrypted innerportion and/or the encrypted outer portion. Thereafter, the UE sends anIAR message 1720 carrying the encrypted outer portion to the SeAN 220.In some embodiments, the UE 215 sends the IAR message 1720 withouthaving received the identity request 1710. The TAR message 1720 mayinclude an unencrypted home network ID (SID). Upon receiving the IARmessage 1720, the SeAN 220 determines a serving network private key(SPrK) based on the unencrypted SID, and decrypts the encrypted outerportion of the IAR message using the SPrK. The SeAN 220 then forwards anauthentication and data request message 1730 carrying the encryptedinner portion, the second copy of the IMSI, and a RAND1 to the HSS 230.The authentication and data request message 1730 may include otherinformation in addition to the encrypted outer portion, such as SeANsecurity capability parameters, the SID, and a NWK Type.

Upon receiving the authentication and data request message 1730, the HSS230 may obtain the KIAR_(ENC) based on the second copy of the IMSI andthe RAND1, and decrypt the encrypted inner portion using the KIAR_(ENC)to obtain the first copy of the IMSI. The HSS 230 may then compare thefirst copy of the IMSI (carried in the encrypted inner portion of theauthentication and data request message 1730) with the second copy ofthe IMSI (carried in an unencrypted outer portion of the authenticationand data request message 1730) to verify the integrity of theauthentication information request message 1730. The HSS 230 may alsotake other steps to validate the authentication and data request message1730. For example, the HSS 230 may compare the COUNTER in the encryptedinner portion with a corresponding COUNTER maintained by the HSS 230 todetermine whether the authentication and data request 1730 is fresh(e.g., not stale). If the validation is successful, then the HSS 230 mayobtain a KIAS_(ENC) based on the IMSI and a random number (e.g., RAND1,RAND2, etc.), generate authentication vectors based on an EPS-AKAprocedure, and send an authentication and data response message 1735carrying the EPS authentication vectors and the KIAS_(ENC) to the SeAN220.

Subsequently, the SeAN 220 encrypts UE specific information using theKIAS_(ENC) to obtain an encrypted portion, which is sent to the UE 215via an IAS message 1750. The encrypted portion of the IAS message 1750may include other information in addition to the UE specificinformation, such as a temporary network identifier and a KSI associatedwith a NAS ciphering algorithm. The IAS message 1750 may further includean unencrypted version of the RAND2. The UE 215 may decrypt theencrypted portion of the IAS messageimo using a KIAS_(ENC), and send asecurity and authentication complete message 1770 to the SeAN 220.

FIG. 18 illustrates frame formats for an embodiment TAR message 1820, anembodiment authentication and data request message 1830, an embodimentauthentication and data response message 1835, and an embodiment IASmessage 1850.

The embodiment IAR message 1820 corresponds to the IAR message 1780 sentfrom the UE 215 to the SeAN 220. In this example, the embodiment IARmessage 1820 includes an encrypted inner portion 1822, an encryptedouter portion 1824, and an SID. The encrypted inner portion 1822 isformed by encrypting a UE_SEC_CAP, a first copy of an IMSI, a first copyof a RAND1, a first copy of a RAND2, and a first copy of a COUNTER usinga KIAR_(ENC). The encrypted outer portion 1824 is generated byencrypting the encrypted inner portion 1822 along with a second copy ofthe IMSI, a second copy of the RAND1, a second copy of the RAND2, and asecond copy of the COUNTER using a SPuK. It should be appreciated thatadditional information may be included in the encrypted inner portion1822 and/or the encrypted outer portion 1824. In one embodiment, a MACsignature generated by computing a hash of the encrypted outer portion1824 using a KIAR_(INT) is also included in the IAR message 1820.

The embodiment authentication and data request message 1830 correspondsto the authentication and data request message 1730 sent from the SeAN220 to the HSS 230. As shown, the embodiment authentication and datarequest message 1830 the encrypted inner portion 1822 from the IARmessage 1820, as well as unencrypted information 1834. The unencryptedinformation 1834 includes the second copy of the IMSI, the second copyof the RAND1, the second copy of the RAND2, and the second copy of theCOUNTER, which were obtained from decrypting the encrypted outer portion1824 of the IAR message 1820 using the SPrK.

The embodiment authentication and data response message 1835 correspondsto the authentication and data response message 1735 sent from the HSS230 to the SeAN 220. As shown, the authentication and data responsemessage 1835 includes a KIAS_(ENC), a KIAS_(INT), the first copy of theCOUNTER, the first copy of the RAND2, the first copy of the IMSI, andAV(s). The first copy of the RAND2 and/or the COUNTER in theauthentication and data response message 1835 may provide replayprotection. In this example the authentication and data response message1835 includes both the RAND2 and the COUNTER. In another example, theauthentication and data response message 1835 includes the RAND2 butexcludes the COUNTER.

The embodiment IAS message 1850 corresponds to the IAS message 1750 sentfrom the SeAN 220 to the UE 215. As shown, the IAS message 1850 includesan encrypted portion 1852 and the RAND2. The encrypted portion 1852 isformed by encrypting a KSI, the AVs, and the COUNTER using theKIAS_(ENC). In some examples, the embodiment IAS message 1850 includes aMAC signature that is generated by computing a hash of the encryptedportion 1852 using the KIAS_(INT).

Embodiments of this disclosure provide methods for performing MASAprotocols. FIG. 19 is a flowchart of an embodiment method 1900 forgenerating an IAR message according to a MASA protocol, as may beperformed by a UE. At step 1910, the UE generates a KIAR_(ENC) based ona pre-provisioned key (K key) and a RAND1. At step 1920, the UE encryptsUE specific information using the KIAR_(ENC) to form an encrypted innerportion. At step 1930, the UE encrypts at least the encrypted innerportion, a RAND1, and an IMSI using a SPuK to form an encrypted outerportion. At step 1940, the UE sends an TAR message carrying theencrypted outer portion and an unencrypted SID to a base station in aserving network.

FIG. 20 is a flowchart of an embodiment method 2000 for processing anIAR message and generating an authentication and data request messageaccording to a MASA protocol, as may be performed by an SeAN. At step2010, the SeAN receives an IAR message carrying an encrypted outerportion and an SID. At step 2020, the SeAN decrypts the encrypted outerportion using a SPrK associated with the SID to obtain at least anencrypted inner portion, a RAND1, and an IMSI. At step 2030, the SeANsends an authentication and data request message carrying the encryptedinner portion, the RAND1, and the IMSI to an HSS.

FIG. 21 is a flowchart of an embodiment method 2100 for processing anauthentication and data request message and generating an authenticationand data response message according to a MASA protocol, as may beperformed by an HSS. At step 2110, the HSS receives an authenticationand data request message from a SeAN in a serving network. Theauthentication and data request message carries an encrypted innerportion, a second copy of a RAND1, and a second copy of an IMSI. In someembodiments, the authentication and data request message includes asecond copy of a RAND2 and/or a second copy of COUNTER.

At step 2120, the HSS obtains a KIAR_(ENC) based on the second copy ofthe IMSI and the second copy of the RAND1. At step 2130, the HSSdecrypts the encrypted inner portion using the KIAR_(ENC) to obtain atleast a first copy of the IMSI, a first copy of the RAND1, and a RAND2.In some embodiments, the HSS compares the first copy of the IMSI, RAND1,RAND2, and/or COUNTER with the second copy of the IMSI, RAND1, RAND2,and/or COUNTER (respectively) to verify the integrity of theauthentication and data request message.

At step 2140, the HSS generates authentication vectors (AVs) based on anEPS-AKA procedure. At step 2150, the HSS obtains a KIAS_(ENC) based onthe IMSI and a RAND2. In some embodiments, steps 2120 and 2150 areperformed in parallel such that the second copy of the IMSI, the secondcopy of the RAND1, and the second copy of the RAND2 are sent from theHSS to the authentication server in the same request message, and theKIAR_(ENC) and KIAS_(ENC) are returned from the authentication server tothe HSS in the same response message. At step 2160, the HSS sends anauthentication and data response message to the SeAN. The authenticationand data response message includes the KIAS_(ENC) the AVs.

In some examples, the UE 215 generates the RAND2, and includes the RAND2in the IAR message. The RAND2 is then used by the HSS 23 o toindependently generate the KIAS_(ENC) and/or the KIAS_(INT). In otherexamples, the HSS 230 independently generates the RAND2, and sends theRAND2 to the authentication server. The authentication server thengenerates the KIAS_(INT) and/or the KIAR_(ENC) based on the RAND2, thek-key and (in some cases) a COUNTER, and returns the KIAS_(INT) and/orthe KIAS_(ENC) to the HSS 230. The HSS 230 then forwards the KIAS_(INT)and/or the KIAS_(ENC) to the SeAN 220, which may use the the KIAS_(ENC)and/or the KIAS_(INT) to generate the IAS message. In such an example,the RAND2 and the COUNTER may be sent to the UE 214 via the IAS message,and the UE may use RAND2, the k-key, and the COUNTER to independentlycompute the KIAS_(ENC) and/or the KIAS_(INT). In an embodiment, aCOUNTER is required to be included in an IAS message for purposes ofreplay protection when the RAND2 is independently generated by the HSS230.

When a COUNTER is included in an authentication and data requestmessage, the HSS may compare the COUNTER with an independent COUNTERmaintained by the HSS to ensure that the COUNTER in the authenticationand data request message exceeds the independent COUNTER maintained bythe HSS. This may confirm that information in the authentication anddata request message is fresh, as well as provide replay protection.Likewise, when a COUNTER is included in an IAS message, the UE maycompare the COUNTER with an independent COUNTER maintained by the UE toensure that the COUNTER in the IAS message exceeds the independentCOUNTER maintained by the HSS. This may confirm that information withinthe IAS message is fresh, as well as provide replay protection.

It should be appreciated that encrypting an IMSI in an IAR message (aswell as other messages) using, for example, a KIAR_(ENC), a SNPuK,and/or a HNPuK serves to at least partially conceal the IMSI frommalicious third parties.

It should be appreciated that a MAC signature may used to provideintegrity protection for the contents of any message described herein.

FIG. 22 illustrates a frame formats for an embodiment IAR message 2220.The embodiment IAR message 2220 includes an encrypted inner portion2222, an outer portion 2224, and a MAC signature 2226. The encryptedinner portion 2222 is formed by encrypting an IMSI and a COUNTER usingan HPuK. The outer portion 2224 includes the encrypted inner portion2222, a UE_SEC_CAP, a RAND1, and an HID. The MAC 2226 is generated bycomputing a hash of the outer portion 2224 using a KIAR_(INT).

Embodiments of this disclosure provide techniques for securelycommunicating an IMSI over the air from a UE to an SeAN, as well as forsecurely validating an unencrypted IMSI that the SeAN receives from thehome network, during authentication protocols. In particular, the UE mayeither encrypt the IMSI assigned to the UE using an IMSI encryption key(K_(IMSIenc)) or compute a hash of the IMSI assigned to the UE using anIMSI integrity key (K_(IMSIint)), and then send the encrypted IMSI orthe hash of the IMSI to the serving network. The encrypted IMSI or hashof the encrypted IMSI may then be used by the SeAN to validate anunencrypted IMSI that was previously received from an HSS in the homenetwork of the UE.

Embodiments techniques for securely communicating an IMSI over the airand/or for securely validating an unencrypted IMSI received from a UE'shome network may be compatible with EPS-AKA protocols. FIG. 23illustrates a protocol diagram of an embodiment communications sequence2300 for authenticating the UE 215 in a wireless network. As shown, thecommunications sequence 2300 begins when the SeAN 220 communicates anidentity request 2310 to the UE 215. Next, the UE 215 communicates anidentity response 2320 to the SeAN 220. The identity response 2320includes an encrypted IMSI, which was generated by using a HPuK toencrypt an IMSI assigned to the UE 215. The identity response 2320 mayalso carry other information, such as an HN ID, etc.

Thereafter, the SeAN 220 communicates an authentication and data request2330 to the HSS 230. The authentication and data request 2330 mayinclude the encrypted IMSI that was carried in the identify response, aswell as other parameters, such as a SN ID and network type (NWK type)parameter.

Upon receiving the authentication and data request 2330, the HSS 23 odecrypts the encrypted IMSI using an HPrK, computes a response parameter(RES) based on a pre-provisioned key (k_key) of the UE as well as otherEPS authentication vectors, and sends an authentication and dataresponse 2335 carrying XRES, an unencrypted IMSI, and the EPSauthentication vectors to the SeAN 220.

Upon receiving the authorization data response 2335, the SeAN 220generates a KSI_(ASME), and sends a user authentication request 2340carrying the KSI_(ASME), as well as a random number and authenticationvector (AUTN), to the UE 215. The UE 215 computes an authenticationresponse (RES) based on the RAND, the AUTN, and a secret key. The secretkey may be a priori information to the UE 215. For example, the secretkey may be a subscriber-specific master key (k_key) stored in aUniversal Subscriber Identity Module (USIM) of the UE 215. The UE 215may then send a user authentication response 2350 carrying the RES tothe SeAN 220. The SeAN 220 may then authenticate the UE 215 by comparingthe RES in the user authentication response 2350 received from the UEwith the RES in the authorization data response 2335 received from theHSS 230.

Thereafter, the SeAN 220 may communicate a security mode command message2360 to the UE 215. The security mode command message 2360 may include aserving network public key (SPuK), and may indentify an integrityprotection algorithm and/or a ciphering algorithm. The UE 215 may usethe integrity protection algorithm to verify the integrity of thesecurity mode command message 2360. After verifying the integrity of thesecurity mode command message 2360, the UE 215 may use the cipheringalgorithm to derive NAS encryption keys. In one embodiment, the UEencrypt the IMSI assigned to the UE using an IMSI encryption key(K_(IMSIenc)) and/or compute a hash of the IMSI assigned to the UE usingan IMSI integrity key (K_(IMSIint)). The K_(IMSIenc) and/or theK_(IMSIint) may be NAS encryption and/or integrity keys. Alternatively,the K_(IMSIenc) and/or the K_(IMSIint) may be derived from the K_(ASME)carried by the security mode command message 2360. As yet anotheralternative, the K_(IMSIenc) and/or the Kimslint may be derived based ona k_key of the UE as well as a COUNTER and RAND carried in the userauthentication request 2340. As yet another alternative, the K_(IMSIenc)and/or the K_(IMSIint) may be the SPuK.

The UE 215 then sends the security mode complete message 2370 to theSeAN 220 to verify that the UE 215 validated the security mode commandmessage 2360, and derived the NAS encryption keys. The security modecomplete message 2370 may include the encrypted IMSI and/or the hash ofthe IMSI, which may be used to validate the unencrypted IMSI receivedfrom the HSS in order to verify that the home network provided accurateinformation. This validation step may be required by a legal orgovernmental agency that has been given authority to track thewhereabouts and/or to monitor the communications of a specific user orUE, particularly in situations where the UE's home network is in aforeign country

When the security mode complete message 2370 includes the encryptedIMSI, the SeAN 220 may validate the unencrypted IMSI received from theHSS by decrypting the encrypted IMSI received from the UE using aK_(IMSIenc) to obtain a decrypted IMSI, and comparing the unencryptedIMSI received from the HSS with the decrypted IMSI to see if they match,in which case the unencrypted IMSI received from the HSS is validated bythe SeAN 220. Alternatively, when the security mode complete message2370 includes the hash of the IMSI, the SeAN 220 may validate theunencrypted IMSI received from the HSS by computing a hash of theunencrypted IMSI received from the HSS using the K_(IMSIint), andcomparing the computed hash with the hash of the IMSI received from theUE to see if they match, in which case the unencrypted IMSI receivedfrom the HSS is validated by the SeAN 220.

Although FIG. 23A depicts the K_(IMSIenc)-encrypted IMSI and/orK_(IMSIint)-signed hash of the IMSI being communicated in the securitymode complete message 2370, it should be appreciated that other optionsare also possible. For example, the K_(IMSIenc)-encrypted IMSI and/orK_(IMSIint)-signed hash of the IMSI may be communicated in the userauthentication response 2350 as shown in FIG. 23B. Furthermore, althoughFIG. 23A depicts the HPuK-encrypted IMSI as being communicated in theidentify response 2320, it should be appreciated that the HPuK-encryptedIMSI can be communicated in other messages as well. For example, theHPuK-encrypted IMSI may be communicated in an Attach request 2322 sentfrom the UE 215 to the SeAN 220 as shown in FIGS. 23C-23D, in which casethe SeAN 220 may return an attach accept 2382 at the end of thesequence.

FIG. 24 illustrates a protocol diagram of an embodiment communicationssequence 2400 for authenticating a UE in a wireless network. As shown,the communications sequence 2400 begins when the SeAN 220 communicatesan identity request 2410 to the UE 215. Next, the UE 215 encrypts anIMSI assigned to the UE using an HPuK. Thereafter, the UE 215 sends anIAR message 2420 carrying an encrypted IMSI, which was generated byusing a HPuK to encrypt an IMSI assigned to the UE 215. It should beappreciate that the IAR message 2420 may also include some or all of theadditional information and/or layers of encryption/integrity protectionthat are included in any of the other IAR messages described in thisdocument, such as the IAR messages described in conjunction with FIGS.4, 5, 11, 12, 17, and 18.

Upon receiving the IAR message 2420, the SeAN 220 forwards anauthentication and data request message 2430 carrying the encrypted IMSIto the HSS 230. It should be appreciate that the authentication and datarequest message 2430 may include some or all of the additionalinformation and/or layers of encryption/integrity protection that areincluded in the corresponding authentication and data request messagesdescribed in conjunction with FIGS. 4, 5, 11, 12, 17, and 18.

Upon receiving the authentication and data request message 2430, the HSS230 may decrypt the encrypted IMSI, and sends an authentication and dataresponse message 2435 carrying an unencrypted version of the IMSI to theSeAN 220. It should be appreciated that the HSS 230 may also computeother parameters (e.g., EPS authentication vectors, encryption/integritykeys, etc.) upon receiving the authentication and data request message2430 from the SeAN 220, and that the authentication and data requestmessage 2430 may include some or all of the information carried by thecorresponding authentication and data request messages described inconjunction with FIGS. 4, 5, 11, 12, 17, and 18.

Subsequently, the SeAN 220 may send an IAS message 2450 to the UE 215.The IAS message 2450 may include some or all of the information carriedby the corresponding IAS messages described in conjunction with FIGS. 4,5, 11, 12, 17, and 18.

Upon receiving the IAS message 2450, the UE 215 may authenticate thenetwork based on information included in the IAS message 2450. The UE215 may then encrypt the IMSI assigned to the UE using an IMSIencryption key (K_(IMSIenc)) and/or compute a hash of the IMSI assignedto the UE using an IMSI integrity key (K_(IMSIint)), and send a securityand authentication complete message 2470 that includes the encryptedIMSI or hash of the IMSI to the SeAN 220. The SeAN 220 may then validatethe unencrypted IMSI received from the HSS based on the unencrypted IMSIand/or hash of the IMSI received from the UE using the K_(IMSIenc)and/or the K_(IMSIint). It should be appreciated that the security andauthentication complete message 2470 may include some or all of theinformation and/or additional layers of encryption/integrity protectionincluded in the corresponding security and authentication completemessages described in conjunction with FIGS. 4, 5, 11, 12, 17, and 18.

FIG. 25 is a flowchart of an embodiment method 2500 for securelytransmitting an IMSI to a serving network, as may be performed by a UE.At step 2510, the UE receives an authentication message from a basestation in a serving network. At step 2520, the UE authenticates theserving network based on the first authentication message. At step 2530,the UE encrypts an IMSI assigned to the UE using a K_(IMSIenc)associated with the serving network. At step 2540, the UE sends theencrypted IMSI to the base station in the serving network.

FIG. 26 is a flowchart of an embodiment method 2600 for securelyvalidating an unencrypted IMSI received from a home network of a UE, asmay be performed by an SeAN. At step 2610, the SeAN receives anunencrypted IMSI from an HSS in a home network of a UE. At step 2620,the SeAN receives an encrypted IMSI from the UE. At step 2630, the SeANdecrypts the encrypted IMSI based on a K_(IMSIenc) associated with theserving network. At step 2640, the SeAN validates the unencrypted IMSIreceived from the HSS when the unencrypted IMSI matches the decryptedIMSI.

FIG. 27 is a flowchart of an embodiment method 2700 for securelytransmitting an IMSI to a serving network, as may be performed by a UE.At step 2710, the UE receives an authentication message from a basestation in a serving network. At step 2720, the UE authenticates theserving network based on the authentication message. At step 2730, theUE computes a hash of an IMSI assigned to the UE using a K_(IMSIint)associated with the serving network. At step 2740, the UE sends the hashof an IMSI to the base station in the serving network.

FIG. 28 is a flowchart of an embodiment method 2800 for securelyvalidating an unencrypted IMSI received from a home network of a UE, asmay be performed by an SeAN. At step 2810, the SeAN receives anunencrypted IMSI from an HSS in a home network of a UE. At step 2820,the SeAN receives a hash of an IMSI from the UE. At step 2830, the SeANcomputes a hash of the unencrypted IMSI received from the HSS based on aK_(IMSIint) associated with the serving network. At step 2840, the SeANvalidates the unencrypted IMSI received from the HSS when the computedhash of the unencrypted IMSI matches the hash of the IMSI received fromthe UE.

Embodiments of this disclosure utilize an IAR_resend flag to triggerre-transmission of an IAR message carrying a K_(IMSIenc)-encrypted IMSIor a K_(IMSIint)-signed hash of the IMSI following the earliertransmission of an IAR message carrying an HPuK-encrypted IMSI.

FIG. 29A illustrates a protocol diagram of an embodiment communicationssequence 2900 for using an IAR_resend flag to trigger re-transmission ofan IAR message carrying a K_(IMSIenc)-encrypted IMSI or aK_(IMSIint)-signed hash of an IMSI by a UE. The identity request message2910, the IAR message 2920, and the authentication and data requestmessage 2930 may be similar to the identity request message 2410, theIAR message 2420, and the authentication and data request message 2430in conjunction with FIG. 24.

Upon receiving the authentication and data request message 2930, theSeAN 220 sends an JAS message 2950 that includes an IAR_resend flag tothe UE 215. The IAR_resend flag may instruct the UE 215 to send a secondIAR message 2922 that includes an K_(IMSIenc)-encrypted IMSI or aK_(IMSIint)-signed hash of an IMSI following authentication of thenetwork. Alternatively, the IAR_resend flag may instruct the UE 215 tosend an K_(IMSIint)-encrypted IMSI or an K_(IMSIint)-signed hash of theIMSI in an Authentication and Security Complete message 2923 followingauthentication of the network as shown in FIG. 29B.

Accordingly, upon receiving the IAS message 2950, the UE 215 mayauthenticate the network based on information included in the IASmessage 2950, and then either encrypt an IMSI assigned to the UE using aSPuK to obtain an K_(IMSIenc)-encrypted IMSI or compute a hash of theIMSI using the K_(IMSIint) to obtain a hash of the IMSI, as well as sendthe IAS message 2922 carrying the K_(IMSIenc)-encrypted IMSI or theK_(IMSIint)-signed hash of the IMSI to the SeAN 220. It should beappreciate that the IAS message 2950 and the IAR message 2922 mayinclude some or all of the additional information and/or layers ofencryption/integrity protection that are included in the respective IASmessage 2450 and IAR message 2420 described in conjunction with FIG. 24.

Upon receiving the IAR message 2922, the SeAN 220 may validate theunencrypted IMSI received from the HSS based on theK_(IMSIenc)-encrypted IMSI or the K_(IMSIint)-signed hash of the IMSIcarried in the IAR message 2922. Although the K_(IMSIenc)-encrypted IMSIor the K_(IMSIint)-signed hash of the IMSI are described as beinggenerated using the SPuK, it should be appreciated that the encryptedIMSI and/or computed hash of the IMSI carried by the IAR message 2922may be generated using any type of K_(IMSIenc) or K_(IMSIint) that isassociated with the serving network.

FIG. 30 is a flowchart of an embodiment method 3000 for securelytransmitting an IMSI to a serving network, as may be performed by a UE.At step 3010, the UE encrypts an IMSI assigned to a UE using HPuK. Atstep 3110, the UE sends an IAR message that includes the HPuK-encryptedIMSI to a SeAN in a serving network. At step 3030, the UE receives anIAS message including an IAR_resend flag from the SeAN. At step 3040,the UE encrypts or computes a hash of the IMSI using a K_(IMSIint) ofthe serving network. At step 3050, the UE re-sends an IAR message thatincludes the K_(IMSIenc)-encrypted IMSI or the K_(IMSIint)-signed hashof the IMSI to the SeAN.

FIG. 31 is a flowchart of an embodiment method 3100 for securelyvalidating an unencrypted IMSI received from a home network of a UE, asmay be performed by an SeAN. At step 3110, the SeAN receives an IARmessage that includes the HPuK-encrypted IMSI from a UE. At step 3120,the SeAN sends the HPuK-encrypted IMSI to HSS At step 3130, the SeANreceives an unencrypted IMSI from the HSS. At step 3140, the SeAN sendsan IAS message including an IAR_resend flag to the UE. At step 3150, theSeAN receives an IAR message including a K_(IMSIenc)-encrypted IMSI or aK_(IMSIint)-signed hash of the IMSI from UE. At step 3150, the SeANvalidates the unencrypted IMSI received from the HSS based on a SPrK andeither the K_(IMSIenc)-encrypted IMSI or the K_(IMSIint)-signed hash ofthe IMSI.

Denial of service attacks can occur when a Man in the Middle (MITM)intercepts an attach request from a UE, and returns an attach reject tothe UE because the attach reject may generally prompt the UE to set aback time, which may be referred to as off timer. Embodiments of thisdisclosure mitigate the likelihood that a MITM will use an attach rejectmessage to perform a denial of service attack by signing the attachreject message with a SPrK. FIG. 32 is a diagram of a communicationssequence 3200 in which a UE unsuccessfully attempts to attach to awireless network. In this example, the UE 215 sends an attach request3210 to an SeAN 220, who is unable to authenticate the UE 215, andreturns an attach reject 3220 to the UE 215. The attach reject 3220prompts the UE 215 to set a back off timer, and the UE 215 is unable toinitiate mobility management signaling prior to expiration of theback-off timer.

As mentioned above, attach reject messages can be exploited by a MITM towage a denial of service attack on a UE. FIG. 33 is a diagram of acommunications sequence 3300 in which a MITM uses an attach rejectmessage to wage a denial of service attack on a UE. In this example, theUE 215 sends an attach request 3310 that is intercepted by a MITM 212,which may be a fake base station (e.g., a malicious third-party posingas a base station). The MITM launches a denial of service attack bysending an attach reject 3320 to the UE 215. The attach reject 3320indicates that the UE 215 could not be authenticated by the network, andprompts the UE 215 to set a back off timer, which may prevent the UE 215from attempting to access another valid base station for a period oftime (e.g., 24 hours, etc.).

Embodiments of this disclosure prevent, or at least inhibit, these typesof attacks by requiring that a UE validate a received attach rejectmessage prior to setting a back off timer. The attach reject message maybe validated based on a MAC signature carried by the attach rejectmessage.

FIG. 34 is a diagram of a communications sequence 3400 in which a UEunsuccessfully attempts to attach to a wireless network. Similar to thecommunications sequence 3200, the UE 215 sends an attach request 3410 tothe SeAN 220, who is unable to authenticate the UE 215, and returns anattach reject 3420 to the UE 215 that indicates that the UE 215 couldnot be authenticated by the network. However, unlike the attach reject3220, the attach reject 3420 includes a MAC signature, which isgenerated by the SeAN by computing a hash function of informationcarried by the attach reject message 3420 using a SPrK associated withthe underlying serving network. Upon reception, the UE 215 attempts tovalidate the attach reject 3420 by processing the MAC signatureaccording to a SPuK assigned to the serving network. The SPrK and theSPuK form a public-private key pair such that processing of a MACsignature using the SPuK will only result in successful validation ofthe attach reject 3420 if the MAC signature was generated using theSPrK. Because the MAC signature carried by the attach reject 3420 wasgenerated using the SPrK, the UE 215 will determine that the attachreject 3420 is valid, and will set a back-off timer.

Requiring validation of attach reject messages using MAC signatures maysignificantly reduce the likelihood of a MITM waging a successful denialof service attack. FIG. 35 is a diagram of a communications sequence3500 in which a MITM unsuccessfully attempts to use an attach rejectmessage to wage a denial of service attack. In this example, the UE 215sends an attach request 3510 that is intercepted by a MITM 212. The MITM212 attempts a denial of service attack by sending an attach reject 3520to the UE 215. However, because the MITM 212 does not have access to theSPrK, the MITM 212 is unable to generate a MAC signature that willresult in a positive validation if processed using the SPuK of theattach reject 3520. As a result, the UE 215 ignores the attach reject3520, instead of setting a backoff timer, thereby thwarting the MITM'sdenial of service attack.

FIG. 36 is a flowchart of an embodiment method 3600 for validatingattach reject messages, as may be performed by a UE. At step 3610, theUE sends an attach request to an SeAN. At step 3620, the UE receives anattach reject message carrying a message authentication code (MAC)signature from the SeAN. At step 3630, the UE attempts to validate thereceived attach reject message by processing the MAC signature carriedby the received attach reject message according to an SPuK assigned tothe serving network. If the UE determines that the attach reject messageis invalid at step 3640, then the UE ignores the attach reject messageat 3650. Alternatively, if the UE determines that the attach rejectmessage is valid at step 3640, then the UE sets a backoff timer based onthe reject message at step 3660.

A similar technique can be used to verify system information messagesreceived from an SeAN. For example, a UE may receive a systeminformation message carrying its own a MAC signature from an SeAN, andattempt to validate the integrity of the received system informationmessage by processing the MAC signature carried by the received systeminformation message according to the SPuK. If the system informationmessage is deemed invalid, then the UE may ignore the received systeminformation message, as well as not make any attempts to connect, orotherwise refuse to connect, to the device (e.g.,Fake base) from whichthe system information message was received. Alternatively, if thesystem information message is deemed valid, then the UE may process thesystem information message accordingly. A system information message maybe a message that is broadcast by a base station over a broadcastchannel, such as a broadcast control channel (BCCH). A few examples ofsystem information blocks are listed in table 1:

TABLE 1 LTE system information blocks Description MIB Carries physicallayer information of LTE cell which in turn help receive further SIs,i.e. system bandwidth SIB1 Contains information regarding whether or notUE is allowed to access the LTE cell. It also defines the scheduling ofthe other SIBs. carries cell ID, MCC, MNC, TAC, SIB mapping. SIB2Carries common channel as well as shared channel information. It alsocarries RRC, uplink power control, preamble power ramping, uplink CyclicPrefix Length, sub-frame hopping, uplink EARFCN SIB3 carries cellre-selection information as well as Intra frequency cell re- selectioninformation SIB4 carries Intra Frequency Neighbors(on same frequency);carries serving cell and neighbor cell frequencies required for cellreselection as well handover between same RAT base stations(GSM BTS1 toGSM BTS2) and different RAT base stations(GSM to WCDMA or GSM to LTE orbetween WCDMA to LTE etc.). Covers E-UTRA and other RATs as mentionedSIB5 Carries Inter Frequency Neighbors(on different frequency); carriesE- UTRA LTE frequencies, other neighbor cell frequencies from otherRATs. The purpose is cell reselection and handover. SIB6 carries WCDMAneighbors information i.e. carries serving UTRA and neighbor cellfrequencies useful for cell re-selection SIB7 carries GSM neighboursinformation i.e. Carries GERAN frequencies as well as GERAN neighborcell frequencies. It is used for cell re-selection as well as handoverpurpose. SIB8 carries CDMA-2000 EVDO frequencies, CDMA-2000 neighborcell frequencies. SIB9 carries HNBID (Home eNodeB Identifier) SIB10carries ETWS prim. notification SIB11 carries ETWS sec. notification

FIG. 37 illustrates a protocol diagram of an embodiment communicationssequence 3700 for securely transmitting a UE-specific ID to a servingnetwork. The identity request message 3710, the IAR message 3720, andthe authentication and data request message 3730 may be similar to theidentity request message 2410, the IAR message 2420, and theauthentication and data request message 2430 described in conjunctionwith FIG. 24.

In some embodiments, the IAR message 3720 further includes a homesecurity policy request indication. The home security policy requestindication may be encrypted along with the IMSI and/or other UE specificinformation using the HPuK.

Upon receiving the authentication and data request message 3730, the HSS230 decrypts the encrypted IMSI, and assigns a home network temporary ID(Home-Temp-ID) to the UE 215. In embodiments where the IAR message 3720further includes a home security policy request indication, the HSS 230also selects or assigns a home network security policy to the UE 215,which may indicate a recommendation as to how often non-access stratum(NAS) or access stratum (AS) security keys should be updated between theUE 215 and the SeAN 220. Thereafter, the HSS 230 sends an authenticationand data response message 3735 that includes the Home-Temp-ID to theSeAN 220. The authentication and data response message 3735 may alsoinclude the home network security policy, as well as some or all of theinformation carried by the corresponding authentication and dataresponse message 2435 described in conjunction with FIG. 24.

Upon receiving the authentication and data response message 3735 , theSeAN 220 sends an IAS message 3750 that includes the Home-Temp-ID and,in some embodiments, the home network (HN_Sec_Pol). In some embodiments,the Home-Temp-ID and/or the home network security policy are encryptedusing an encryption key, such as a KIASenc. It should be appreciate thatthe IAS message 3750 may include some or all of the additionalinformation and/or layers of encryption/integrity protection included inthe IAS message 2450 described in conjunction with FIG. 24.

Upon receiving the IAS message 2450, the UE 215 may authenticate theserving network, and send a message 3770 that includes the Home-Temp-IDto the SeAN 220. In one embodiment, the message 3770 is an attachrequest message. In another embodiment, the message 3770 is a securityand authentication complete message, in which case the message 3770 mayinclude all or some of the information and/or additional layers ofencryption/integrity protection included in the corresponding securityand authentication complete message 2400 described in conjunction withFIG. 24.

FIG. 38 illustrates frame formats for an embodiment IAR message 3820, anembodiment authentication and data request message 3830, an embodimentauthentication and data response message 3835, and an embodiment IASmessage 3850.

The embodiment IAR message 3820 corresponds to the IAR message 3780 sentfrom the UE 215 to the SeAN 220. In this example, the embodiment IARmessage 3820 includes an encrypted inner portion 3822, an encryptedouter portion 3824, and an SID. The encrypted inner portion 3822 isformed by encrypting an IMSI assigned to the UE 215 and a home networksecurity policy request (HN_Sec_Pol_Req) indication using a KIAR_(ENC).It should be appreciated that other information may also be encryptedalong with the IMSI and the HN_Sec_Pol_Req indication when forming theencrypted inner portion 3822, including all or some of the informationin the respective encrypted inner portions 1222, 1822 described inconjunction with FIGS. 12 and 18. The encrypted outer portion 3824 maybe generated in a similar fashion and/or include some or all of theinformation in the respective encrypted outer portions 1224, 1824described in conjunction with FIGS. 12 and 18.

The embodiment authentication and data request message 3830 correspondsto the authentication and data request message 3730 sent from the SeAN220 to the HSS 230. As shown, the embodiment authentication and datarequest message 3830 includes the IAR message 3820, as well as an HID.

The embodiment authentication and data response message 3835 correspondsto the authentication and data response message 3735 sent from the HSS230 to the SeAN 220. As shown, the authentication and data responsemessage 3835 includes the encrypted inner portion 3822 carried by theIAR message 3820, as well additional information 3834 such as aKIAS_(ENC), a Home-TEMP-ID, and an HN_Sec_Pol.

The embodiment IAS message 3850 corresponds to the IAS message 3750 sentfrom the SeAN 220 to the UE 215. As shown, the IAS message 3850 includesan encrypted portion 3852, which is formed by encrypting thehome-temp-ID and the HN_Sec_Pol using a KIASenc. It should beappreciated that other information may also be encrypted along with thehome-temp-ID and the HN Sec Pol when forming the encrypted portion 3852,including some or all of the information in the respective encryptedportions 1252, 1852 described in conjunction with FIGS. 12 and 18.Additionally, the embodiment IAS message 3850 may include additional,non-encrypted information, including some or all of the informationcarried outside the encrypted portions 1252, 1852 of the IAS messages1250, 1850 described in conjunction with FIGS. 12 and 18.

FIG. 39 is a flowchart of an embodiment method 3900 for securelytransmitting a UE-specific ID to a serving network, as may be performedby a UE. At step 3910, the UE encrypts an IMSI assigned to a UE usingHPuK. At step 3110, the UE sends an IAR message that includes theHPuK-encrypted IMSI to an SeAN in a serving network. At step 3930, theUE receives an IAS message including a home network temporary ID(Home-Temp-ID). At step 3940, the UE sends an attach request to the SeANthat includes the Home-Temp ID. message that includes theK_(IMSIenc)-encrypted IMSI or the K_(IMSIint)-signed hash of the IMSI tothe SeAN.

Embodiments of this disclosure provide techniques for facilitating NASand/or AS layer security negotiation between UEs and the servingnetwork. FIG. 40 illustrates a protocol diagram of an embodimentcommunications sequence 4000 for securely negotiating NAS and/or ASlayer security parameters. In this example, the UE 215 transmits anattach request 4022 to the SeAN 220 that includes UE-specific AS layersecurity capabilities (e.g., AS ciphering algorithms supported by the UE215) and/or UE-specific NAS layer security capabilities (e.g., NASciphering algorithms supported by the UE 215). The SeAN 220 responds bysending a User Authentication Request 4040 that includes SN-specific NASlayer security capabilities to the UE 215 (e.g., NAS cipheringalgorithms supported by the UE 215). In some embodiments, the UserAuthentication Request 4040 also includes access network specific(AN-specific) AS layer security capabilities, such as, inter alia,agreed upon encryption and/or integrity protection algorithms. The UE215 then generates a NAS layer encryption key and a NAS layer integrityprotection key based on the SN-specific NAS layer security capabilities.The NAS layer encryption key may then be used to encrypt contents of theNAS security mode complete message 4070, and the NAS layer integrityprotection key may be used to generate a MAC signature of the contentsof the NAS security mode complete message 4070, prior to the UE 215sending the NAS security mode complete message 4070 to the SeAN 220. TheSeAN 220 may independently generate the NAS layer encryption key and theNAS layer integrity protection key, and use those independentlygenerated keys to decrypt and validate the NAS security mode completemessage 4070.

Additionally, the UE 215 may receive an access stratum (AS) securitymode command 4080 from the base station 210 that includes access networkspecific (AN-specific) AS layer security capabilities (e.g., ASciphering algorithms supported by the base station 210). If theAN-specific AS layer security capabilities were included in the userauthentication request 4040, then the AS security mode command 4080 maynot be communicated, or may be communicated without the AN-specific ASlayer security capabilities. The UE 215 then generates an AS layerencryption key and an AS layer integrity protection key based on theAN-specific AS layer security capabilities. Similar to the NAS layerkeys, the AS layer encryption key may then be used to encrypt contentsof the AS security mode complete message 4090, and the AS layerintegrity protection key may be used to generate a MAC signature of thecontents of the AS security mode complete message 4090, prior to the UE215 sending the AS security mode complete message 4090 to the basestation 220. Similar to the SeAN 220, the base station 210 mayindependently generate the AS layer encryption key and the AS layerintegrity protection key, and use those independently generated keys todecrypt and validate the AS security mode complete message 4090.

FIG. 41 illustrates a protocol diagram of an embodiment communicationssequence 4100 for securely negotiating NAS layer security parameters. Inthis example, the UE 215 transmits an IAR message 4120 to the SeAN 220that includes UE-specific AS layer security capabilities and/orUE-specific NAS layer security capabilities. The SeAN 220 responds bysending an IAS message 4150 that includes SN-specific NAS layer securitycapabilities to the UE 215. The IAS message 4150 may also includeSN-specific AS layer security capabilities. The UE 215 then generates aNAS layer encryption key and a NAS layer integrity protection key basedon the SN-specific NAS layer security capabilities. The NAS layerencryption key may then be used to encrypt contents of the security andauthentication complete message 4170, and the NAS layer integrityprotection key may be used to generate a MAC signature of the contentsof the security and authentication complete message 4170, prior to theUE 215 sending the security and authentication complete message 4170 tothe SeAN 220. The SeAN 220 may independently generate the NAS layerencryption key and the NAS layer integrity protection key, and use thoseindependently generated keys to decrypt and validate the security andauthentication complete message 4170. When the IAS message 4150 includesSN-specific AS layer security capabilities, the UE 215 may generate anAS layer encryption key and an AS layer integrity protection key basedon the AN-specific AS layer security capabilities, which may be used toencrypt, as well as provide integrity protection for (e.g., compute MACsignatures, etc.), wirless transmissions between the UE 215 and the basestation 210.

FIG. 42 is a flowchart of an embodiment method 4200 for NAS layersecurity parameter negotiation, as may be performed by a UE. At step4210, the UE receives SN-specific NAS security capabilities from an SeANin a serving network. At step 4220, the UE generates NAS layer keysaccording to the SN-specific NAS security capabilities. At step 4230,the UE encrypts and/or integrity protects an authentication messageusing the NAS layer keys. At step 4240, the UE sends theencrypted/integrity-protected authentication message to the SeAN.

FIG. 43 is a diagram of an embodiment method 4300 for NAS layer securityparameter negotiation, as may be performed by an SeAN. At step 4310, theSeAN receives UE-specific NAS security capabilities from a UE. At step4320, the SeAN generates NAS layer keys according to the UE-specific NASsecurity capabilities. At step 4330, the SeAN receives anencrypted/integrity-protected authentication message from the UE. Atstep 4340, the SeAN decrypts the encrypted/integrity-protectedauthentication message using the NAS layer keys.

FIG. 44 is a diagram of an embodiment method 4400 for NAS layer securityparameter negotiation, as may be performed by a UE. At step 4410, the UEreceives SN-specific AS security capabilities from a base station in aserving network. At step 4420, the UE generates AS layer keys accordingto the SN-specific AS security capabilities. At step 4430, the UEencrypts and/or integrity protects an authentication message using theAS layer keys. At step 4440, the UE sends theencrypted/integrity-protected authentication message to the basestation.

FIG. 45 is a diagram of an embodiment method 4500 for NAS layer securityparameter negotiation, as may be performed by a base station. At step4510, the base station receives UE-specific AS security capabilitiesfrom either the UE or an SeAN. At step 4520, the base station generatesAS layer keys according to the UE-specific AS security capabilities. Atstep 4530, the base station receives an encrypted/integrity-protectedauthentication message from the UE. At step 4540, the base stationdecrypts the encrypted/integrity-protected authentication message usingthe AS layer keys.

FIG. 46 illustrates a block diagram of an embodiment processing system4600 for performing methods described herein, which may be installed ina host device. As shown, the processing system 4600 includes a processor4604, a memory 4606, and interfaces 4610-4614, which may (or may not) bearranged as shown in FIG. 46. The processor 4604 may be any component orcollection of components adapted to perform computations and/or otherprocessing related tasks, and the memory 4606 may be any component orcollection of components adapted to store programming and/orinstructions for execution by the processor 4604. In an embodiment, thememory 4606 includes a non-transitory computer readable medium. Theinterfaces 4610, 4612, 4614 may be any component or collection ofcomponents that allow the processing system 4600 to communicate withother devices/components and/or a user. For example, one or more of theinterfaces 4610, 4612, 4614 may be adapted to communicate data, control,or management messages from the processor 4604 to applications installedon the host device and/or a remote device. As another example, one ormore of the interfaces 4610, 4612, 4614 may be adapted to allow a useror user device (e.g., personal computer (PC), etc.) tointeract/communicate with the processing system 4600. The processingsystem 4600 may include additional components not depicted in FIG. 46,such as long term storage (e.g., non-volatile memory, etc.).

In some embodiments, the processing system 4600 is included in a networkdevice that is accessing, or part otherwise of, a telecommunicationsnetwork. In one example, the processing system 4600 is in a network-sidedevice in a wireless or wireline telecommunications network, such as abase station, a relay station, a scheduler, a controller, a gateway, arouter, an applications server, or any other device in thetelecommunications network. In other embodiments, the processing system4600 is in a user-side device accessing a wireless or wirelinetelecommunications network, such as a mobile station, a user equipment(UE), a personal computer (PC), a tablet, a wearable communicationsdevice (e.g., a smartwatch, etc.), or any other device adapted to accessa telecommunications network.

In some embodiments, one or more of the interfaces 4610, 4612, 4614connects the processing system 4600 to a transceiver adapted to transmitand receive signaling over the telecommunications network. FIG. 47illustrates a block diagram of a transceiver 4700 adapted to transmitand receive signaling over a telecommunications network. The transceiver4700 may be installed in a host device. As shown, the transceiver 4700comprises a network-side interface 4702, a coupler 4704, a transmitter4706, a receiver 4708, a signal processor 4710, and a device-sideinterface 4712. The network-side interface 4702 may include anycomponent or collection of components adapted to transmit or receivesignaling over a wireless or wireline telecommunications network. Thecoupler 4704 may include any component or collection of componentsadapted to facilitate bi-directional communication over the network-sideinterface 4702. The transmitter 4706 may include any component orcollection of components (e.g., up-converter, power amplifier, etc.)adapted to convert a baseband signal into a modulated carrier signalsuitable for transmission over the network-side interface 4702. Thereceiver 4708 may include any component or collection of components(e.g., down-converter, low noise amplifier, etc.) adapted to convert acarrier signal received over the network-side interface 4702 into abaseband signal. The signal processor 4710 may include any component orcollection of components adapted to convert a baseband signal into adata signal suitable for communication over the device-side interface(s)4712, or vice-versa. The device-side interface(s) 4712 may include anycomponent or collection of components adapted to communicatedata-signals between the signal processor 4710 and components within thehost device (e.g., the processing system 4600, local area network (LAN)ports, etc.).

The transceiver 4700 may transmit and receive signaling over any type ofcommunications medium. In some embodiments, the transceiver 4700transmits and receives signaling over a wireless medium. For example,the transceiver 4700 may be a wireless transceiver adapted tocommunicate in accordance with a wireless telecommunications protocol,such as a cellular protocol (e.g., long-term evolution (LTE), etc.), awireless local area network (WLAN) protocol (e.g., Wi-Fi, etc.), or anyother type of wireless protocol (e.g., Bluetooth, near fieldcommunication (NFC), etc.). In such embodiments, the network-sideinterface 4702 comprises one or more antenna/radiating elements. Forexample, the network-side interface 4702 may include a single antenna,multiple separate antennas, or a multi-antenna array configured formulti-layer communication, e.g., single input multiple output (SIMO),multiple input single output (MISO), multiple input multiple output(MIMO), etc. In other embodiments, the transceiver 4700 transmits andreceives signaling over a wireline medium, e.g., twisted-pair cable,coaxial cable, optical fiber, etc. Specific processing systems and/ortransceivers may utilize all of the components shown, or only a subsetof the components, and levels of integration may vary from device todevice.

Although the description has been described in detail, it should beunderstood that various changes, substitutions and alterations can bemade without departing from the spirit and scope of this disclosure asdefined by the appended claims. Moreover, the scope of the disclosure isnot intended to be limited to the particular embodiments describedherein, as one of ordinary skill in the art will readily appreciate fromthis disclosure that processes, machines, manufacture, compositions ofmatter, means, methods, or steps, presently existing or later to bedeveloped, may perform substantially the same function or achievesubstantially the same result as the corresponding embodiments describedherein. Accordingly, the appended claims are intended to include withintheir scope such processes, machines, manufacture, compositions ofmatter, means, methods, or steps.

What is claimed is:
 1. A method for secure authentication, the methodcomprising: receiving, by a Security Anchor Node (SeAN) in a servingnetwork, an unencrypted International Mobile Subscriber Identity (IMSI)from a home subscriber server (HSS) in a home network of a userequipment (UE); receiving, by the SeAN, an encrypted IMSI or a hash ofan IMSI from the UE; and validating the unencrypted IMSI received fromthe HSS in accordance with either the unencrypted IMSI received from theUE and an IMSI encryption key (K_(IMSIenc)) or the hash of the IMSIreceived from the UE and an IMSI integrity key (K_(IMSIint)).
 2. Themethod of claim 1, wherein validating the unencrypted IMSI received fromthe HSS comprises: decrypting the encrypted IMSI received from the UEusing the K_(IMSIenc) to obtain a decrypted IMSI; and validating theunencrypted IMSI received from the HSS when the unencrypted IMSI matchesthe decrypted IMSI.
 3. The method of claim 1, wherein validating theunencrypted IMSI received from the HSS comprises: computing a hash ofthe unencrypted IMSI received from the HSS using the K_(IMSIint); andvalidating the unencrypted IMSI received from the HSS when the computedhash of the unencrypted IMSI matches the hash of the IMSI received fromthe UE.
 4. The method of claim 1, wherein the K_(IMSIenc) or theK_(IMSIint) is a NAS encryption or integrity key.
 5. The method of claim1, wherein the K_(IMSIenc) or the K_(IMSIint) is derived based on anNG-K_(ASME).
 6. The method of claim 1, wherein the K_(IMSIenc) or theK_(IMSIint) is an IAS encryption or integrity key (K_(IASenc))
 7. Themethod of claim 1, wherein the K_(IMSIenc) or the K_(IMSIint) is aserving network private key (SPuK).
 8. A Security Anchor Node (SeAN)comprising: a processor; and a non-transitory computer readable storagemedium storing programming for execution by the processor, theprogramming including instructions to: encrypt, or otherwise compute ahash of, an International Mobile Subscriber Identity (IMSI) assigned toa user equipment (UE) using an IMSI encryption key (K_(IMSIenc)) or anIMSI integrity key (K_(IMSIint)) associated with a serving network; andsend the encrypted IMSI or the Hash of the IMSI to a base station in theserving network.
 9. A method for secure authentication, the methodcomprising: encrypting, by a user equipment (UE), an InternationalMobile Subscriber Identity (IMSI) of the UE using home network publickey (HPuK) associated with a home network of the UE to obtain anHPuK-encrypted IMSI; sending, by the UE, a first initial authenticationrequest (IAR) message carrying the HPuK-encrypted IMSI to a SecurityAnchor Node (SeAN) in a serving network; receiving, by the UE, aninitial authentication response (IAS) message from the SeAN, the IASmessage including an IAR message resend flag; and in response toidentifying the IAR message resend flag in the IAS message, encrypting,or otherwise computing a hash of, the IMSI using an serving networkpublic key (SPuK) to obtain an K_(IMSIenc)-encrypted IMSI or anK_(IMSIint)-signed hash of the IMSI, and sending a second IAR messagethat includes the K_(IMSIenc)-encrypted IMSI or the K_(IMSIint)-signedhash of the IMSI to the SeAN. 17×2. The method of claim 17, where in theIAR resend flag instruct the UE to send IMSI encrypted using the SN SPuKin the Security and Authentication Complete message.
 10. A userequipment (UE) comprising: a processor; and a non-transitory computerreadable storage medium storing programming for execution by theprocessor, the programming including instructions to: encrypt anInternational Mobile Subscriber Identity (IMSI) of the UE using homenetwork public key (HPuK) associated with a home network of the UE toobtain an HPuK-encrypted IMSI; send a first initial authenticationrequest (IAR) message carrying the HPuK-encrypted IMSI to a SecurityAnchor Node (SeAN) in a serving network; receive an initialauthentication response (IAS) message from the SeAN, the IAS messageincluding an IAR message resend flag; and in response to identifying theIAR message resend flag in the IAS message, encrypt, or otherwisecompute a hash of, the IMSI using an serving network public key (SPuK)to obtain an K_(IMSIenc)-encrypted IMSI or an K_(IMSIint)-signed hash ofthe IMSI, and sending a second IAR message that includes theK_(IMSIenc)-encrypted IMSI or the K_(IMSIint)-signed hash of the IMSI tothe SeAN.
 11. A method for secure authentication, the method comprising:sending, by a user equipment (UE), an attach request message to aSecurity Anchor Node (SeAN) in a serving network, the attach requestmessage requesting access to the serving network; receiving, by the UE,an attach reject message indicating the attach request has been rejectedby the SeAN, the attach reject message carrying a message authenticationcode (MAC) signature; attempting to validate the received attach rejectmessage by processing the MAC signature carried by the received attachreject message according to a serving network public key (SPuK) assignedto the serving network; and ignoring the received attach reject messageupon determining that the attach reject message is invalid.
 12. Themethod of claim11, wherein the SPuK belongs to a public-private key pairassociated with the serving network, and wherein the signed attachreject message can only be successfully validated using the SPuk whenthe underlying attach reject message was signed using a serving networkprivate key (SPrK) of the public-private key pair.
 13. The method ofclaim 11, further comprising: setting, by the UE, a back-off timeraccording to the attach reject message upon determining that the attemptto validate the attach reject message signature using the SPuK issuccessful, the UE being unable to initiate mobility managementsignaling prior to expiration of the back-off timer.
 14. The method ofclaim 11, wherein attempting to validate the integrity of the receivedattach reject message by processing the MAC signature carried by thereceived attach reject message according to the SPuK comprises:generating, by the UE, a separate MAC signature by computing a hashfunction of information carried by the attach reject message accordingto the SPuK; and comparing the MAC signature generated by the UE withthe MAC signature carried by the attach reject message.
 15. The methodof claim 11, further comprising receiving, by the UE, a systeminformation message from the SeAN, the system information messagecarrying its own a MAC signature; attempting to validate the integrityof the received system information message by processing the MACsignature carried by the received system information message accordingto the SPuK; and ignoring the received system information message upondetermining that the system information message is invalid.
 16. A userequipment (UE) comprising: a processor; and a non-transitory computerreadable storage medium storing programming for execution by theprocessor, the programming including instructions to: send an attachrequest message to a Security Anchor Node (SeAN) in a serving network,the attach request message requesting access to the serving network;receive an attach reject message indicating the attach request has beenrejected by the SeAN, the attach reject message carrying a messageauthentication code (MAC) signature; attempt to validate the receivedattach reject message by processing the MAC signature carried by thereceived attach reject message according to a serving network public key(SPuK) assigned to the serving network; and ignore the received attachreject message upon determining that the attach reject message isinvalid.
 17. A method for secure authentication, the method comprising:encrypting, by a user equipment (UE), an International Mobile SubscriberIdentity (IMSI) using a home network public key (HPuK) associated with ahome network of the UE; sending, by the UE, an initial authenticationrequest (IAR) message carrying the encrypted IMSI to a Security AnchorNode (SeAN) in a serving network, the encrypted IMSI being relayed fromthe SeAN to a home subscriber server (HSS) without being decrypted;receiving, by the UE, an initial authentication response (IAS) messagecarrying a home network temporary identifier (Home-Temp-ID) from theSeAN, the Home-Temp-ID having been assigned to the UE by the HSS; andsending, by the UE, a subsequent attach message to the SeAN, thesubsequent attach message carrying the Home-Temp-ID.
 18. The method ofclaim 17, wherein the IAS message further includes aHome-UE-Security-Policy assigned to the UE by the HSS, theHome-UE-Security-Policy indicating how often non-access stratum (NAS) oraccess stratum (AS) security keys should be updated.
 19. A userequipment (UE) comprising: a processor; and a non-transitory computerreadable storage medium storing programming for execution by theprocessor, the programming including instructions to: encrypt anInternational Mobile Subscriber Identity (IMSI) using a home networkpublic key (HPuK) associated with a home network of the UE; send aninitial authentication request (IAR) message carrying the encrypted IMSIto a Security Anchor Node (SeAN) in a serving network, the encryptedIMSI being relayed from the SeAN to a home subscriber server (HSS)without being decrypted; receive an initial authentication response(IAS) message carrying a home network temporary identifier(Home-Temp-ID) from the SeAN, the Home-Temp-ID having been assigned tothe UE by the HSS; and send a subsequent attach message to the SeAN, thesubsequent attach message carrying the Home-Temp-ID.
 20. A method forsecure authentication, the method comprising: sending, by a userequipment (UE), a first authentication message carrying UE-specificnetwork access stratum (NAS) security capabilities of the UE to aSecurity Anchor Node (SeAN) in a serving network; and receiving, by theUE, a second authentication message from the SeAN, the secondauthentication message carrying NAS layer encryption algorithm supportedby the SeAN according to at least the UE-specific NAS securitycapabilities included in the first authentication message.
 21. Themethod of claim 20, wherein the UE-specific NAS security capabilitiesinclude a NAS encryption algorithm, a NAS integrity protectionalgorithm, an RRC encryption algorithm, an RRC integrity algorithm, auser plane encryption algorithm, a user plane integrity algorithm, anIMSI concealment algorithm, or combinations thereof.
 22. A userequipment (UE) comprising: a processor; and a non-transitory computerreadable storage medium storing programming for execution by theprocessor, the programming including instructions to: send a firstauthentication message carrying UE-specific network access stratum (NAS)security capabilities of the UE to a Security Anchor Node (SeAN) in aserving network; and receive a second authentication message from theSeAN, the second authentication message carrying NAS layer encryptionalgorithm supported by the SeAN according to at least the UE-specificNAS security capabilities included in the first authentication message.23. A method for secure authentication, the method comprising:receiving, by a user equipment (UE), a first authentication messagecarrying serving network specific (SN-specific) network access stratum(NAS) security capabilities of a serving network from a Security AnchorNode (SeAN) in the serving network; generating NAS layer encryption keysaccording to the SN-specific NAS security capabilities; and sending, bythe UE, a second protected authentication using the NAS layer encryptionand integrity keys to the SeAN.
 24. A user equipment (UE) comprising: aprocessor; and a non-transitory computer readable storage medium storingprogramming for execution by the processor, the programming includinginstructions to: receive a first authentication message carrying servingnetwork specific (SN-specific) network access stratum (NAS) securitycapabilities of a serving network from a Security Anchor Node (SeAN) inthe serving network; generate NAS layer encryption keys according to theSN-specific NAS security capabilities; and send a second protectedauthentication using the NAS layer encryption and integrity keys to theSeAN.